Please follow the below steps to generate and integrate the MaxMind License Key with
Register using link https://www.maxmind.com/en/geolite2/signup
Navigate to Services > License Key area in MaxMind account. You can click here to directly access the page https://www.maxmind.com/en/accounts/current/license-key
Click on 'Generate new license key' button.
Select 'No' for message 'Old versions of our GeoIP Update program use a different license key format. Will this key be used for GeoIP Update?'
Generate the License Key and keep it safe, This is the only time you will be able to access license key once it is created. Don't worry you can create new keys if needed.
Once you get the License key navigate to WordPress Dashboard > WPAdCenter > Settings > Advanced > Geo Targeting Settings and add your key
Thats it. You have successfully integrated your MaxMind License key with WPAdCenter Pro and now you choose to display ads based on the user location.