I already have a domain name that I want to use as well as buying one through HolidaySiteBuilder. What should I do?

Holiday Site Builder allows you to point domains registered with other domain registrars to your Holiday Site Builder site.

There are two steps to adding previously registered domains or domains registered with other registrars:
1) You will have to change the name servers using the other domain registrar's control panel to:
ns1.stellus.co.uk
ns2.stellus.co.uk
2) Enter the domain in the form on the Domain Management page so HolidaySiteBuilder knows about your domain.