Requesting a cPanel/WHM license to be added to your account is easy. Simply login to your account manager at http://www.greengeeks.com/login/ and submit a ticket with your request to have your license added for your VPS. Our support team will license this for you.
Once the cPanel/WHM license has been issued, you will be required to set up the initial cPanel setup wizard. For documentation on this, please see: WHM Initial Setup
For full documentation:
cPanel: cPanel Documentation
WHM: WHM Documentation