What do I need to do in CPANEL if I'm not going to map sub domains?

Hi, I'm a newb and this is my first time using the plugin. I think I've set it all up properly but have a few questions:
1. If I don't plan on allowing users to map a sub domain they may have, do I need to anything in CPANEL for each regular domain they want to map?
2. Is it all automatic? Do I just put in the domain the user has registered somewhere else, and it will map to my dedicated IP...all automatically?
3. Does anyone use the eNom service? Do you find that customers will actually buy a domain name from within your sites? It seems the service charges hefty fees. Not sure about that though. Thanks.