We include a style sheet in a webpage with the link element. link is an empty element and goes inside the head element.

Add a link element inside the head element.

<html>
<body>
  <h1>Water Puns</h1>
  <p>Why does water never laugh at jokes?
  It's not a fan of dry humor.</p>
</body>
</html>]]>

Make sure to pick <link>.