Enable Google Drive API & Authorize Client ID

1. Go to Navigation Menu > APIs & Services > Dashboard.
2. Click on ENABLE APIS AND SERVICES.
3. Search for the Google Drive API and enable it.
4. Go to https://admin.google.com and log in with the same Google Account.
5. Click Security in Admin Console.
6. In Security page, scroll down and click API controls.
7. In API controls page, click MANAGE DOMAIN WIDE DELEGATION.
8. Click Add new and add the Client ID from step 12 of Create Google Service Account.



9. Add https://www.googleapis.com/auth/drive to OAuth scope and click AUTHORIZE.