add classpath 'com.google.gms:google-services:3.1.0' to build.graddle of your project/platform/android:

    buildscript {
        repositories {
            jcenter()
        }

    	dependencies {
    		classpath "com.android.tools.build:gradle:2.2.3"
            classpath 'com.google.gms:google-services:3.1.0'
    	}
    }

copy the google-services.json to your your project/platform/android folder