Navigate to Administration>Manage Users
Click on the user name of who you want to grant rights
Click on User Rights
Expand the section you want to grant rights.
Check boxes to grant rights. To grant all rights in this section, click the Grant All Rights buttons. Also you can select one right for everything by clicking the box at the top of the row or pick and choose which rights to grant.
NOTE: Users have to log out and back in to see changed rights granted.