This theme has built-in support for UIkit-3 icons: https://uikitstacks.com/documentation/icon/
Use the snippet below for a basic icon implementation:
<span uk-icon="icon: check; ratio: 1.0"></span>
Icon with link
Add a link to the icon with the snippet below, replacing the # with your link:
<a href="#" uk-icon="icon: heart; ratio: 1.0"></a>
Note that examples of icons are included in the tutorial project.