This stack is using the Font Awesome icon font, by Dave Gandy. Altogether Font Awesome provides more than 300 icons as scalable vector graphics, meaning that they look great in all displays resolutions.
Use a Text or HTML stack with the uk-icon-* class as shown in the example below. The icons behave just like text, you can change the colors and sizes in the Customizer stack.
Icons with links
Add links as the example below, replacing the # with your link.
<a href="#" class="uk-icon-github"></a>
Add the classes uk-icon-small, uk-icon-medium and uk-icon-large to make the icon bigger.