I am a beginner Android developer and I am working on my first Android game We all had the experience of Android games. When we enter the game, game ask us to connect via Gmail to it can save the progress of the game for us. Now what should I do if I want to add something like this to my game?
You have to use google play services for this purpose. As there are many scenarios for login in and saving data from your game, it would be better you go through the following documents for sign-in and saving game data.
As you didn't mention that what you using to develop your game, the installation instructions can't be given specifically. For Android Native, you have to add a dependency on your build.gradle. For game engines, you may have to use packages/libraries developed for that purpose.