- Enable the feature in Settings > Account settings > Integration > Automatic user login after API code transfer, or (if you are creating a new account via API) add an additional parameter in account: integration_fast_login:true
- call our program URL with 2 parameters: https://yourPrefix.yourwebsite.com?api_token=API_TOKEN&fast_login=yes - a user opening this URL will be automatically logged in (https is a requirement)