How to make News Aggregation app with Firebase?

I’m making a news aggregation like app (a Reddit clone because it isn’t a Reddit clone). This is what my code so far looks like:

<!DOCTYPE html>
		<title>Journalists Notebook</title>
		<link rel="stylesheet" href="">
       <form name="news" method="POST">
        <input title="SoloLearn Username" name="username" placeholder="Your username?" required>
        <input title="Article Topic/Header" name="header" placeholder="Topic/Header Article" required>
        <textarea title="All the news for your article..." rows="5" columns="5" placeholder="Article" required></textarea>
        <button type="submit" class="btn btn-info" name="send">PUBLISH</button>

How or where can I add the firebase connecting?