This article will explain how to order add ons for Plesk.
Login to your 123-reg control panel
Click on the Manage link under the VPS section.
Click on the Manage button next to your VPS.
Click on the Add ons tab.
Click on the Add link next to the add on you wish to order.
Select one of the following options shown for your add on, then click on the Add to basket button.
Complete the payment details form and purchase your order.