You can check out my plugin construct.net/en/construct-2/addons/415/play-games-leaderboard
I have made clear documentation and also example (.capx)
And you have to sign-in to play games as soon as the layout starts.
There are also many play games plugin available but all were using deprecated GoogleAPIs, so I made this out. As of now it only supports leaderboard.
If you have any issues with it do mail me :)