CSS can and should be added in a seperate file from the working Html file. That way the html would look clean.
style.css
p {
margin: 20%;
border: 1px solid blue;
border-radius: 50%;
height: 200px;
width: 200px;
}
home.html
<!DOCTYPE html>
<html lang="en">
<head>
<title>CSS in Seperate file</title>
<link rel="stylesheet" href="./styles/styles.css" >
</head>
<body>
<div>
<p>WW</p>
</div>
</body>
</html>
styles.css. Then add a reference.