The below program will do so
<html>
<head>
<title>Our First Program Using ReactJS</title>
<script src="build/react.js"></script>
<script src="build/react-dom.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.23/browser.min.js"></script>
</head>
<body>
<div id="mainContainer"></div>
<script type="text/babel">
ReactDOM.render(
<h1>Message from RNA Team - "Welcome to ReactJS World"</h1>,
document.getElementById('mainContainer')
);
</script>
</body>
</html>