You can download the Firebase config file or Firebase config object for each of your project's apps from the Project settings page. You need this config file or object to configure your app to use Firebase.
You may need to access your config file or object after the initial registering of the app with Firebase if you're setting up a new environment or you're not the member who originally registered the app.
Get config file for your Android app
To download the config file for a Firebase Android app:
1. Sign in to Firebase, then create your project.
Click on Create a project and follow the steps.
Add a name for your project and select the appropriate settings, then click on Create project.
2. Click , then select Project settings.
3. In the Your apps card, select the platform for the app you want created.
If you already have apps, select the package name of the app for which you need a config file.
Follow the required steps to add Firebase to your Android app. Here are the steps:
Step 1 - Register app
Step 2 - Download config file
Step 3 - Add Firebase SDK
Step 4 - Run your app to verify installation
4. Click google-services.json, then add it to your app.