Include the line below inside the <head> of your HTML file. Place it before any other site page stylesheets.
<link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/gh/shakrmedia/petal@0.11.1/dist/petal.min.css">
The CDN link will provide the latest minified pre-built version of Petal with default settings.
Now you can use all the Petal classes and styles in your project's HTML file.
If you want to customize options and personalize Petal style for your project, you will need to build Petal manually. Head to Custom Building for guide and recommendations on integrating Petal into your project.