Simply navigate to the product that you want to feature and click on it to open it.
Below the product's name and type selectors, you'll find a navigation bar - click "Detailed Info." This will bring you to the detailed information section of that particular product.
Here, you'll find the buttons to apply a Product Highlight. Click which one you want to use, and hit "Save Changes" in the upper right hand corner.
Your product's highlight will now be applied on the menu.
Product Highlights are applied at the location level. So, if you apply a Highlight to a product at Location A, Location B won't see that Highlight unless they also apply it to the same product. This is done so that managers at each location have complete flexibility over which products are featured in their stores.
Your BoardLink is likely running an old version of the menu app. To pull the most recent version, simply restart your BoardLink by toggling the inline power switch or unplugging the unit and plugging it back in.