After registering an additional domain you will be able to manage them individually by switching between them
The domain that you are currently managing is indicated in the top right hand corner of your Control Panel
To change the domain that you are currently managing simply click on the down arrow to show a list of your domains. Click the domain you wish to manage. You'll notice your domain has changed in the Control Panel. You are now able to manage the settings and services for that domain!
You can also click on Your Domains from the drop down menu to see a list of your domains and their services
You will be taken to a page that will show all of your domains and the services that you have for each one!