Just log in as SuperUser in Mumble, right-click root and edit ACL. You can add channels/assign admin accounts etc. It's just been a group of max 10 friends for me so I've never really needed to do too much except add members admin and add a few channels. But I've been able to do everything I've needed to from there. Hope this helps :)
OK, I've tried it but can't figure out how. How do I create user accounts and their passwords?