Can someone direct me to the instructions for answering and receiving my 3 user accounts via the superadmin account?

Can someone direct me to the instructions for answering and receiving my 3 user accounts via the superadmin account?

I'm a new user, and recently set up 3 accounts (users?) for my own use - admin, karen, info. I'd like to be able to access emails and send emails from all three accounts. Can someone direct me to the instructions for accomplishing this?
Thanks in advance,
Karen