3. Get the SHA-1 from your application (required for Android only).
The SHA-1 is specified in App Settings -> Platform specific options.
See screenshot 3 for more details:
After you have done this, you won't need to update the application, or add to it any data.
NOTE! For other Authentication options may be required to copy the Client ID and add it to the appropriate details in the app. The Client ID is provided once you click on Create in the OAuth client ID page. Note that you may need also to create the URL Scheme based on your Client ID. The URL Scheme is the actual reversed Client ID.
These details can also be found when you access your OAuth 2.0 client IDs for the app in Developers Console. After you have added all the details and published your application you may need to fill the OAuth consent screen in your Google account. For more details consider to follow the Google regulations on this case.
Note that if you add the Messenger page type in Application Settings a new section will appear named "Social Authentication" You'll need to provide the related keys there.
googleoauth clientId="123-textletters.apps.googleusercontent.com"