Currently Plumrocket uses 2 approaches for licensing:
1. Serial Key Activation:
Once you have purchased and set up your Plumrocket Magento Extension - normally it will not require setting up the serial key, since it will be automatically pasted into according field under configuration section of Extension. If so - you will see a green tick next to serial key. However, if not - you will need to find your serial key and paste it manually. More information on serial key setup can be found in this Wiki Article.
2. License Installation:
If you need to use the license file for the extension you have purchased, please follow the step-by-step instructions outlined in Plumrocket Wiki Article.
Please note that not all plumrocket extensions or Magento themes require serial keys/licenses. Free Magento extensions and all Magento themes from Plumrocket Inc do not require serial key setup/license installation at all.