<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css">
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/jquery.slim.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/umd/popper.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js"></script>
</head>
<body>
<div class="jumbotron text-center">
<h1>My First Bootstrap Page</h1>
<p>Resize this responsive page to see the effect!</p>
</div>
</body>
</html>
place this html code and Bootstrap 4 work on your website.
https://onlinepage.in/coding/bootstrap-4-html-code-instant-bootstrap-4-setup/
please visit here for boostrap code