Create Firebase App: https://console.firebase.google.com/

Adnroid Setup:

Go to the android/ directory of your react-native project

Create a file named local.properties with this line:

sdk.dir = /Users/USERNAME/Library/Android/sdk

Aadd google-services.json to FirebaseAuth/android/app

iOS Setup

For iOS app add GoogleService-Info.plist to FirebaseAuth/ios/FirebaseAuth

To Run

open terminal, change directory to project

$ npm install

$ react-native run-android