1. First you need to Log in to your Plesk control panel.
2. Once logged into the Plesk control panel you can set up your domains hosting.
To add a new domain go to Subscriptions – Add New Subscription.
3. Enter in the new domain name. Specify a FTP Username and Password (Make a note of these and keep in a safe place.) then set the Service Plan to Unlimited and hit OK
4. That's it! Your new domain has been added into your VPS and you can now go ahead and configure it as necessary.