Hello all, n00b question here. Just what you needed, right? ;)

We're in the building and testing stage and advanced perms are on. I would like to add test users to groups named Webmaster and Creator, which will eventually have access to page editing and/or Composer. The Administrators group has permission to Assign Groups to User. However, when I try to add the users, access is denied. I tried to add the superuser to Assign Groups to User by name, but it didn't seem to take. I previously added another admin successfully, but I believe it was before I enabled advanced perms.

Any input appreciated. Thank you very much!