Yes, you can! You can use your existing domain. It’s easy to do. In the signup process you will have four options to add a domain. Select the option that says “I will use my existing domain and update my nameserver.”

Add your domain here and complete the sign-up process. Next login to the account where your domain is hosted and update your domain nameserver. You must point it to us.

This article provides an overview for updating your nameserver.

How to update my nameserver

Note that your domain registrar might have a different interface – but the steps are pretty much the same.