When creating managed Unit, I can't get the MU to show up on the webpage unless explicitly apply a user. Group doesn't work.

When creating  managed Unit, I can only get the MU to show up on the webpage if I explicitly apply my user account with the Builtin\AR Server Security - Manage Units Container.  If I apply a group that I'm in, it doesn't show.  Of course, if I apply Authenticated user all the way down, it's visibly but I dont' want that. Any suggestions?  I'm new to the product.  Can't find anything in the Admin guide about this. It says I can apply a user or group.