There are two ways to use MaterializeCSS, either you can download the files on your system or use the files from CDN (Content Delivery Network).
Download files
npm install materialize-css
bower install materialize
Include From CDN
Include minifed CSS in the head section:
<!-- Compiled and minified CSS -->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/materialize/0.97.7/css/materialize.min.css">
Include Javascript file in the Body section, just before the closing body tag.
<!-- Compiled and minified JavaScript -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/materialize/0.97.7/js/materialize.min.js"></script>