Getting my movie clip to jump and stay on stage

Question

For an assignment and just to let you know I am a newbie.
My stage size is 640x 480y
I have placed an image of a chicken on my stage over the background and (with help) I have moving clouds.
I have gotten to move my chicken up, down, left and right using the arrow keys.
I can get it to jump on its own but then I can't seem to assign it to a specific key.
I also can't seem to keep it on the stage.
import flash.display.*;
import flash.events.*;
          /* created a container containing an instance
             of my background image & used addChild to
             place it one the stage*/
var myBackground:BackGround = new BackGround();
    addChild(myBackground);
          // Moving clouds//
var myCloud:MyCloud;
         //Created a loop that pushes 6 clouds to the stage//
for (var i:Number = 0; i<6; i++)
    myCloud = new MyCloud();
      addChild(myCloud);
        /*Creates a random value varible containing
          Math.random() which returns a number 0 <=
          And <1 so,will never get 1*/
    var randomValue: Number = Math.random()*1;
        /*Creates a random collection of clouds drawn
          moving in various positions of the stage width.
          And the x & y Scale of the clouds are set randomly*/      
     myCloud.x = Math.random()*stage.width;
     myCloud.scaleX = myCloud.scaleY = randomValue;       
         /*Creates an event for the myCloud to listen out for
           function to get the MovieClip (all clouds) flyby when
           entering the frame*/
    myCloud.addEventListener(Event.ENTER_FRAME, flyBy);
    function flyBy(event:Event):void
          // Modular function for all the clouds to move//
    MovieClip(event.currentTarget).x +=6;
    if (event.target.x> stage.stageWidth)
        event.target.x = 0;
    addChild(myCloud);
// The Hen and Key Board functions //
var myHen:ChickHen = new ChickHen;
addChild(myHen);
//The x and y positioning co ordinates for the hen//
myHen.x = 230;
myHen.y = 350;
var distance:int = 100;
//leftmost position based upon boundary box
var leftArrow:int = (myHen.x - myHen.width /2) + 100;
//rightmost position based upon boundary box
var rightArrow:int = (myHen.x + myHen.width / 2) - 100;
//topmost position based upon boundary box
var upArrow:int = (myHen.y - myHen.height / 2) + 100;
/* Add keyboard listeners to the stage */
stage.addEventListener(KeyboardEvent.KEY_DOWN,move);
function move(event:KeyboardEvent):void
/* Use a switch to determine which key was pressed */
var key = event.keyCode;
switch(key)
case 39:
myHen.x +=distance;
break;
case 37:
myHen.x -=distance;
break;
case 38:
myHen.y -=distance;
break;
case 40:
myHen.y +=distance;
break;
I used the following method to make it jump  but I don't know how to assign this to a specific key:
stage.addEventListener(KeyboardEvent.KEY_DOWN, jump);
stage.addEventListener(KeyboardEvent.KEY_UP, land);
function jump (event:KeyboardEvent): void
  myHen.y -=120
function land (event:KeyboardEvent): void
  myHen.y +=120

Answer 1

Thank you for the reply,
I've tried your and Ned's suggestion and I know I'm doing something really stupid.... but I can't see it?
Now when I move the hen to the image it disappears. 
import flash.display.*;
import flash.events.*;
import flash.ui.Keyboard;
          /* Variables to contain and create instances of buttons, images and background*/
var myHen:ChickHen = new ChickHen();
var buttonPlay:playButton = new playButton();
var myBackground:BackGround = new BackGround();
var buttonHelp:help = new help();
var myBake: bake = new bake();
var myCut: cut = new cut();
var myMake: make = new make();
var myWater: water = new water();
var myPlant: plant = new plant();        
var pointer:int = 1;
addChild(myBackground); 
addChild(myHen); 
addChild(buttonPlay);
addChild(buttonHelp);
addChild(myBake);
addChild(myCut);
addChild(myMake);
addChild(myWater);
addChild(myPlant);
/*These MovieClips are transparent until the "play" button is pressed*/   
myBake.alpha =0;
myCut.alpha = 0;
myMake.alpha = 0;
myWater.alpha = 0;
myPlant.alpha = 0;
/*--The x and y positioning co ordinates of my MovieClips & buttons ---*/
myHen.x = 230;
myHen.y = 350;
myBake.x = 590;
myBake.y = 157;
myCut.x = 345;
myCut.y = 145;
myMake.x = 214;
myMake.y = 170;
myWater.x = 95;
myWater.y = 160;
myPlant.x = 466;
myPlant.y = 167;
buttonPlay.x = 190;
buttonPlay.y = 204;
buttonHelp.x = 446;
buttonHelp.y = 230;
myPlant.order = 1;
myWater.order = 2;
myCut.order = 3;
myMake.order = 4;
myBake.order = 5;
/*------Introduction Page------*/
/*--creating an EventListener to listen out for when the play button is pressed---*/     
buttonPlay.addEventListener(MouseEvent.CLICK,startGame);
     function startGame(event:MouseEvent):void
        myBake.alpha =1;
        myCut.alpha = 1;
        myMake.alpha = 1;
        myWater.alpha =1;
        myPlant.alpha = 1;
        buttonPlay.alpha = 0;
        buttonHelp.alpha = 0;
/* event listener has  been removed once the play button is transparent*/
     if (buttonPlay.alpha == 0)
     buttonPlay.removeEventListener(MouseEvent.CLICK,startGame);
          /* Variable to contain image of cloud*/
var myCloud:MyCloud;
         /*Created a loop that pushes 6 clouds to the stage*/
     for (var i:Number = 0; i<6; i++)
         myCloud = new MyCloud(); /*instance of cloud*/
        /*Creates a random value varible containing
          Math.random() which returns a number 0 <=
          And <1 so,will never get 1*/
var randomValue: Number = Math.random()*1;
        /*Creates a random collection of clouds drawn
          moving in various positions of the stage width.
          And the x & y Scale of the clouds are set randomly*/      
        myCloud.x = Math.random()*stage.width;
        myCloud.scaleX = myCloud.scaleY = randomValue;       
         /*Creates an event for the myCloud to listen out for
           function to get the MovieClip (all clouds) flyby when
           entering the frame*/
    myCloud.addEventListener(Event.ENTER_FRAME, flyBy);
    function flyBy(event:Event):void
          // Modular function for all the clouds to move//
    MovieClip(event.currentTarget).x +=6;
     if (event.target.x> stage.stageWidth)
        event.target.x = 0;
        addChild(myCloud);
   /*---This EventListener and function is to keep the hen on the stage----*/
   myHen.addEventListener(Event.ENTER_FRAME,keepMovieClipOnStage);
    function keepMovieClipOnStage(event:Event):void
      if(myHen.x<10)
      myHen.x=100;
     if(myHen.x>stage.stageWidth)
      myHen.x=230;
var distance:int = 80;
   /*leftmost position based upon boundary box*/
var leftArrow:int = (myHen.x - myHen.width /2) + 50;
   /*rightmost position based upon boundary box*/
var rightArrow:int = (myHen.x + myHen.width / 2) - 50;
   /*topmost position based upon boundary box*/
var upArrow:int = (myHen.y - myHen.height / 2) + 50;
       /* Add keyboard listeners to the stage */
    stage.addEventListener(KeyboardEvent.KEY_DOWN,move);
      function move(event:KeyboardEvent):void
      /* Use a switch to determine which key was pressed */
     var key = event.keyCode;
      switch(key)
         case 39:
         myHen.x +=distance;
         break;
         case 37:
         myHen.x -=distance;
         break;
   stage.addEventListener(KeyboardEvent.KEY_DOWN, jump);
   stage.addEventListener(KeyboardEvent.KEY_UP, land);
     function jump (event:KeyboardEvent): void
     switch(event.keyCode)
      case Keyboard.UP:
      myHen.y =120;
      myHen.x +=10;
function land (event:KeyboardEvent): void
       myHen.y =350;
   /*------ end hen and key board functions-----*/
myWater.addEventListener(Event.ENTER_FRAME, collision);
function collision (event:Event): void    
     (myHen.hitTestObject (myWater))
     if (pointer == myWater.order)
         myWater.visible = false;
        pointer++;
      } /*this is what it looks like*/