I already have purchase a domain with someone else. How do I sign up?

From HostBaby Wiki

Situation

So, you own a domain name already. Great! You simply need to sign up for the free trial at Hostbaby.com for web hosting, and use the domain name you already own. Doing so won't affect any hosting / registration situation you're currently in; this will only allow you to try our hosting services with your domain name.

What will happen

If you already own a domain name, you can still certainly sign up for hosting here at Hostbaby.com

Once you sign up, one of our customer service representatives will review your signup, see that you already own your domain name, and will send you instructions on how to access our services without affecting your current hosting/registration configuration.

This will allow you to preview what we have to offer during our 30 day free trial. If you like our services, great! We'll instruct you how to modify your domain name registration to host your website with us. If you prefer not to host here, no problem! Simply close your account by filling out the "Close Account" form in the Member's section of Hostbaby.com.