Learning Laravel and my Bootstrap header isn't appearing horizontally

<nav class="navbar navbar-default">
  <div class="container-fluid">
    <div class="navbar-header">
      <a href="#" class="navbar-brand">Laravel Guide</a>
      <ul class="nav navbar-nav">
        <li><a href="#">Blog</a></li>
        <li><a href="#">About</a></li>
      </ul>
    </div>
  </div>
</nav>

I'm not sure why my code isn't working. I'm new to bootstrap and laravel. The video I'm watching has this code specifically in it and I'm copying the code to understand its functionality as I work on my own project.

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">

This is the link at the top of my code.

via Chebli Mohamed