This tutorial video is a step by step process to add Google Sign In to your game with the Master Collection Plugin by Chadori (https://www.constructcollection.com/) and integrate it with Playfab.
This allows users to use their Google account to link their saved game play on Playfab and be able to log in with it across devices / platforms.
Hope this helps people who are struggling through figuring out how to implement this all in google play console / cloud platform!
FoozleCC