A user can be added to a group two ways:

1. During the definition and creation of the User ID. See Create User ID.
2. From the User's session. 

To add a user to a group using the User's session:

1. Advanced: System Admin> User Management> User's.
2. Using filters, find a specific user.
3. Click Add to Group.  Be patient!  When adding a user to a group all the permissions of that group will be copied into the User IDs record.