Installing SSL Certificate on Google App Engine
- Log in to Google Cloud → "Products & Services" → "App Engine".
- Settings → "SSL Certificates" → "Upload a new certificate" → "Add a new SSL Certificate".
- Upload certificate.crt, cabundle.crt, privatekey.pem.
- Choose the domains to secure under "Enable SSL for the following custom domains" and Save.
Continue at Step 3 in the plugin.