I have a project with 1 module and 2 applications. The module is used for code parts that both applications uses. Of course I have separate google-services.json files in the
Go to firebase console
Create a new project.
Then go and click on Add Firebase to your Android app
Add Package name (from AndroidManifest.xml)
Then it'll generate google-services.json
Copy this file and add it to (i) your project root (ii) your project>app
Sync project (Tools -> Android -> Sync Project with Gradle Files)
Hope this will help to you :)