Transferring a domain name is different than pointing your domain name to WebStarts using nameservers or an A record. If you are looking to use a domain name that you already own without transferring registration, check out this tutorial.
If you are looking to transfer registration of the domain name from your current registrar to WebStarts, you will need to first add the domain name to your WebStarts account. This can be done by clicking the ‘add domain name’ icon at the top of your account. Once the domain name is added to your account, contact your current domain registrar and request a transfer. They will unlock the domain name and provide you with an authorization code. Send that code to email@example.com and request a domain transfer.