Moving iPhoto from internal hard drive to external hard drive

Question

My computer is almost full, so bought a new external hard drive to move my iPhoto to.  Here is the problem.
I followed the directions on quitting iPhoto and by going into the Pictures folder, I copied to the external hard drive.  That worked just fine.
I tested the pictures and videos on the external and work.  Same events, amount of pictures, movies, etc.
So I went into my internal iPhoto and deleted one event (not an important one thankfully).  I then went into my external hard drive and opened up iPhoto.  The event was also deleted there.  Why?
I only have one library for the photos.  I also have version 8.1.2.
How can I delete the photos on my internal to free up space on my computer, but have it not affect the photo library on the external hard drive?  The only reason I purchased an external hard drive was to move my photos from my internal and free up much needed space.
Did I do something wrong, or miss a step?  If somebody can help me in "very easy" instructions on how to fix this problem, I would greatly appreciate it!  I am not a computer whiz, so need the instructions given to me very simply.
Thank you!

Answer 1

This is really quite simple.
There are two possibilities here only:
1. You keep opening the same Library.
or
2. You failed to make a copy at all.
Stop doing this:
I am opening both by double clicking on my internal or my external
Do this instead:
Hold down the option (or alt) key key and launch iPhoto. From the resulting menu select 'Choose Library'
You will see two Libraries Listed.
If you don't then you didn't copy it properly.
If you do, then select the internal Library. Make a deletion.
Then repeat:
Hold down the option (or alt) key key and launch iPhoto. From the resulting menu select 'Choose Library'
This time select the external. Is the change reflected there?