After installing wp2print, you must activate your license. When the license is not yet activated, you will see the following warning message displayed at the top of your administrative pages:
After purchasing wp2print, you will receive an activation code from Print Science or from your reseller. Activating the license code is simple: Visit wp2print/Settings and select the "License" tab. Enter the activation code, and press the button "Activate".
This video illustrates the entire process of activating your license: