To install an app from outside the Play Store, you'll need to download its APK file and allow installations from unknown sources. Third-party app stores are installed like any other app, but then ...

C:\Program Files\Google\Play Games Developer Emulator\current\emulator ... adb install command followed by the directory and ...

you can only install Android apps and games visible in the Play Games beta storefront. Google won’t let you install APK files or even regular Android apps. For that, we’ll have to turn to ...