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: https://www.extendware.com
  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.