How do new users sign up and use their own domain?

Hi guys,

Hope you guys are having a good weekend. I finished setting up Pro Sites and maybe I didn't set up properly but how do people sign up and use their own domain? Does this have to be done with another plugin like Gravity Forms User Sign Up and then Pro Sites takes over? If so, how do I set up Gravity Forms to work with Pro Sites and Domain Mapping.

Thanks,
Andy GH