Chart.js can be included in several different ways:
NPM
Run the following command on your NPM project directory
npm install chart.js --save
CDN
Include a script tag in your HTML linking to the chart.js CDN
<html>
<body>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.1.6/Chart.bundle.min.js"></script>
</body>
</html>
Latest version can be found at cdnjs.com/libraries/Chart.js.
Local Copy
A local copy can also be hosted on your server. You can get the lasted version from their GitHub.
<html>
<body>
<script type="text/javascript" src="/Path/To/Chart.bundle.min.js"></script>
</body>
</html>
For more information about getting chart.js installed see www.chartjs.org/docs/.