Here are the steps to add Domain to your license. 

  1. Log into my account and select " My Downloadable Products".
  2. Located your purched extension and enter your domain address including the protocol, example:
  3. Click on the UPDATE button to generate my licens code.
  4. Mark the license code and copy it ot your clip board.
  5. Access your Magento backend and access Stores > Settings > Configuration > Extendware Extension > General Settings
  6. Paste your license code and apply it.