Ok, no problem!
During the online signup process with Mr.Host, you’ll have a few options for your domain registration settings.
If you want to register a NEW domain to go along with your hosting, then select “Register this domain for me”
If you already have a domain, then select “I already have this domain…”, and then select the option that says you want to transfer registrars to Mr.Host.
If you already have an account with Mr.Host, then you can register new domains, and transfer in existing domains, via the Customer Control Panel.