How to authenticated and guest users

I want the following setup:

  • muc_max_occupants = 1

–> Guest can join a room and are alone by default

Now I have a whitelist that all users authenticated are allowed to join.

I can register users via prosodyctl.
How can registered users login? Sounds stupid, but where can they enter their credentials to be authenticated?
How can I make sure that guest users aren’t asked for a login and auth. users can login?