In order to add extra bandwidth or dispace to your hosting package, you need to log in to your client area account at https://www.fast2host.com/clientarea.php
Select My Products & Services from the menu.
Click on More Options next to the hosting package for which you want to add more bandwidth or diskspace.
Scroll down and select the link Click to view available add-ons.
You can then select from the list of presented add-ons available for your hosting package.