add stylesheet to html
<!-- Linking External Style Sheets -->
<head>
<link rel="stylesheet" href="css/style.css" />
</head>
<!-- Embedded Style Sheets -->
<head>
<style>
body {
background-color: YellowGreen;
}
h1 {
color: blue;
}
p {
color: red;
}
</style>
</head>
<!-- Inline Styles -->
<h1 style="color: red; font-size: 30px">This is a heading</h1>
<p style="color: green; font-size: 18px">This is a paragraph.</p>
<div style="color: green; font-size: 18px">This is some text.</div>