You will first need to integrate your game with the ArmorGames APIs, so that ArmorGames users can sign in to your game. Please refer to these resources if you need help with this:
Control Panel Setup
When you setup your Connection to use the ArmorGames authentication type, you need to provide the ArmorGames API Key for your game.
To authenticate an ArmorGames user, you need to get the user id and auth token from the game page.
Once you have those, you can call Authenticate like this: