You must config FCM settings so your site would be able to push notification using Google Firebase. Follow the instruction below for how to do it: Add Firebase to your web app.
- For Project Server Key: you can found your server key in your Firebase App console > Project Settings > Cloud Messaging
- For Snippet Code: you can found it in your Firebase App console > Project Settings > General > Add Firebase to your web app

Video Guide:

April 9, 2018