1. For new installation, showing with problems like "app unavailable" or some other error, first install the app from Google Play Store, you dont have to download the full app, just cancel it. Then install the apk.
Remember, Don't use the mod during tutorial and use a strong internet connection.
2. For those signed apks with previous version data with no gplay logins,
Just install the new apk over the previous game. Don't uninstall it if you want to keep data.( I believe it will show as an update)
That's all.
After update apk installation, open the game . If it asks for downloading data inside the game do it. (Always use strong internet connection).
Happy gaming