wriote css in the header code example
Example 1: add stylesheet html
<link rel="stylesheet" type="text/css" href="style.css">
Example 2: how to add a css file in html
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="styles.css">
</head>
<body>
<h1>This is a heading</h1>
<p>This is a paragraph.</p>
</body>
</html>