This article will explain how you can activate a new IP address for your 123-reg VPS.
In the VPS section, click on the Manage link.
Click on the Manage button next to the VPS you wish to configure.
Click on the IP tab.
Click on the Assign a new IP address button.
Select a domain to assign to the IP from the drop down list. Then click on the Assign Domain button.
Click on the Yes button to confirm.