Final answer:
To embed an external .css file, use the element within the section of the HTML document, specifying 'stylesheet' as the rel attribute value and providing the correct path to the CSS file in the href attribute.
Step-by-step explanation:
To embed an external .css file into an HTML document, the <link> element is used within the <head> section of the HTML document. This link element should specify the rel attribute as "stylesheet" and the href attribute as the path to the CSS file. Here's an example:
<head>
<link rel="stylesheet" href="styles/style.css">
</head>
Make sure that the path in the href attribute correctly points to the location of the CSS file that you want to link to your HTML document.