Howdy,
This is easy enough to do. Install the site on your staging server like your normally would. When the site is ready and you are in the process of transferring come back to this site. Notice the Account Central link in the upper right. Hover over that, then click on licenses. You will see each of your purchased licenses for all your sites. For any license that you need to transfer, just click the disconnect button. Then on the new server you can input the license key and verify it just like you did on the staging server the first time.
Does that make sense? We try to make the process very seamless.
– Brook