Check out example codes for "css without separate file". It will help you in understanding the concepts better.
Code Example 1
<link rel="stylesheet" type="text/css" href="mystyle.css">
Code Example 2
<html>
<head>
<link rel="stylesheet" type="text/css" href="Name.css">
</head>
<body>
.
.
.
</body>
Code Example 3
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="mystyle.css">
</head>
<body>
<h1>This is a heading</h1>
<p>This is a paragraph.</p>
</body>
</html>
Code Example 4
<link rel="stylesheet" type="text/css" href="mystyle.css">
Code Example 5
just add any style inside the first <p> or other element tag using style=" ;"
<p style="font-size: xx-large;">test</p>
Learn ReactJs, React Native from akashmittal.com