Sharepoint 2013 assign users to a group

Question

In a test sharepoint 2013 sandbox area that is setup for myself and runs in the cloud,  I am working with 3 test accounts.
I would like to know how to assign these 3 test accounts to the same group.
I would think I need this in a site mailbox.
I am asking this question since this is my first project using sharepoint and no one else in my company is using sharepoint yet.
Thus can you do the following:
1. I would like to know how to assign these 3 test accounts to the same group hopefully in a site mailbox.
2. How would I access this group when I am assigning the task using 'start a process'?

Answer 1

you can achieve this using server side object model which fetches the data from server as below link:
http://sharepoint.stackexchange.com/questions/104465/create-sharepoint-group-and-assign-permission-sharepoint-online
http://www.c-sharpcorner.com/UploadFile/sagarp/programmatically-how-to-add-assign-user-to-a-user-group-in/
you can achieve the same using client side object model which hits server only once using execute query method as below:
http://www.c-sharpcorner.com/Blogs/8244/add-user-to-the-group-in-sharepoint-2010-using-client-object.aspx
try this link for second question hope it wiil be useful:
http://community.spiceworks.com/how_to/show/66248-restrict-a-sharepoint-task-to-its-assigned-user-group
Please mark as answer if you find it useful else vote for it if it is close to answer..happy sharepointing