To include an external stylesheet, one uses the following syntax, which must be in the head of the document, and "style.css" can be replaced with whatever your css file is named:
<link href="style.css" rel="stylesheet" type="text/css">
Again, in the head of the document for the stylesheet, but this time the syntax is different. To include a stylesheet for a particular web page, use the following syntax:
<style type="text/css">
body { color: red; }
p { font-size: smaller; }
</style>
To change the style of just one tag's contained elements, which is not recommended because it does not separate visual layout from content, use the following syntax:
<p style="color:blue;">Blue text.</p>
Blue text.