Add-ons can be purchased via the Client Billing Portal located at: https://www.webecs.com/client/clientarea.php
1) Once logged into the portal, select "My Products & Services". You will then see a listing of all of your currently purchased packages.
2) In the far right column, you will see a "View Details" icon, select this and you will be taken to the product details page.
3) Near the bottom of this page you will see "Account Addons" and a link "Click to view available addons". Click the link to view a list of the addons that you can purchase for the selected product.