Pre-compile configuration

Open the android project in latest Android Studio released and if it asked to update gradle plugin agree.

Android app relies on Firebase for purposes of Free SMS Authentication, Notifications & Crashlytics. So with one single setup of Firebase into your project app is ready to compile.

On the firebase project you have created during backend installation do as Google Instructs you on their official documentation (Only Step 4 & 5):

With google-services.json file being in place you should go ahead and open environment.xml file in values folder of shared project.

Put a google Maps API key for Android app in google_maps_key variable.

Now search for and open the file namedBackend.ktand put your server address here.

As an standard procedure when sending app for release you would have to create a sign key and for every subsequest release use that key to sign your app. This key has an SHA-1 signature that you would need to put on Firebase project console. Don't forget to do that as instructed on link above.

Don't worry about security Firebase API were used to verify correct app connects to server.

Compile APK

With above steps done correctly you are ready to compile app and send for Play Store release. Use Generate Signed APK in Build menu to create the apk.