1. Go to Google Developers Console and connect with your Google account
  2. Click Create project and give it a name
  3. Once the process is finished, click on the newly created project
  4. Go to APIS & AUTH / Credentials
  5. Click Create new Client ID
  6. Give your domain name as Authorized Javascript origins and the above Callback URL as Authorized redirect URI
  7. Now copy the Client ID and the Client Secret to Google2Piwigo configuration
  8. You're done!