Checkout the video tutorial at my YouTube Channel
Create a HTML page and include JS code from Firebase Web Console
Be sure to paste the configuration code into your web page as described.
<script src="https://www.gstatic.com/firebasejs/4.12.1/firebase.js"></script>
<script>
// Initialize Firebase
var config = {
apiKey: "xxxxxxxxxxxxxxxxxxxxxxx",
authDomain: "xxxxxxxxxx.firebaseapp.com",
databaseURL: "https://xxxxxxxxxxxxxx.firebaseio.com",
projectId: "xxxxxxxxxxxxxxxxxxxxxxx",
storageBucket: "xxxxxxxxxxxxxxxxxxxxxxx.appspot.com",
messagingSenderId: "xxxxxxxxxxxxxxxxxxxxxxx"
};
firebase.initializeApp(config);
// your code
//...
</script>