You can not "attach" a SASS/SCSS file to an HTML document.
SASS/SCSS is a CSS preprocessor that runs on the server and compiles to CSS code that your browser understands.
There are client-side alternatives to SASS that can be compiled in the browser using javascript such as LESS CSS, though I advise you compile to CSS for production use.
It's as simple as adding 2 lines of code to your HTML file.
<link rel="stylesheet/less" type="text/css" href="styles.less" />
<script src="less.js" type="text/javascript"></script>
