how to write a css file code example

Example 1: add stylesheet html

<link rel="stylesheet" type="text/css" href="style.css">

Example 2: external style sheet

<link rel="stylesheet" type="text/css" href="mystyle.css">

Example 3: how to add style to p tag in html

<h1 style="color:blue;">This is a Blue Heading</h1>
<!DOCTYPE html>
<html>
<head>
<style>

 body {background-color: powderblue;}
h1   {color: blue;}
p    {color: red;}

</style>
</head>
<body>

<h1>This is a 
 heading</h1>
<p>This is a paragraph.</p>

</body>
</html>