Hi, I had to learn first to understand which widget comes where; you can see the locations here: https://appfinite.com/topic/epik-widgets-guide/
Once you know on which widget you want to work on, you go on your WP Dashboard to APPEARANCE>>WIDGETS where you move with drag and drop the needed widgets onto the right side, which is the Feature-side.
You can drag a “Text” widget there, and then add the content inside of that widget. Genesis Child themes don’t come with Shortcodes (it’s not good practice, see here – http://justintadlock.com/archives/2011/05/02/dealing-with-shortcode-madness ). What they’ve done here is added the html that you can use inside of the widget areas. The html used in the demo can be found at the top of the Epik Forum – https://appfinite.com/forum/epik-theme-support/ (they are the yellow highlighted sticky posts)
@arjanbakker There is a Read Me file in your theme folder that explains how to get the basics setup. It also includes a link to the tutorials for this theme which is located at the top of the Epik Forum. They are the Yellow Sticky Posts at the top. There are also General tutorials in the menu above – https://appfinite.com/tutorials/ which also explains how and where to setup the slider.