When you're ready to point your domain at your ProSite account, simply update your nameservers to the following:
Your domain should start working with your account within a few hours.
If you'd prefer to manage your domain elsewhere and not point your domain at our nameservers, you can also point your domain at your ProSite account using a CNAME record in your DNS Zone.
Simply add a CNAME for the www record, pointing to sitebuilder.kualo.com.
www CNAME sitebuilder.kualo.com
You may need to ask your domain provider for assistence with this. If the DNS zone already contains a www record, this should be removed first.