Helpy includes an icon picker that uses the Glyphicon set.  This is a fairly basic icon set that will work for most uses.  However, you can use other icon sets that use CSS to describe the icon to be shown.  To do this, you will not have the benefit of an icon picker, but if you know the icon you wish to use, the setup is pretty simple, especially if you want to use font-awesome 5, which is included in the Helpy package.

1. Determine the iconset you wish to use
   
   
2. Install the icon css using the settings > design > header css . This is not needed for Font Awesome, unless you are using the pro version.
   
   
3. Access the settings for the category you wish to use a custom icon for
   
   
   
   
4. On the line "icon," add "null" to cancel out the Glyphicon, then the selectors for your new icon selection.
   
   ie. null fas fa-question
   
   
5. When finished, it should look like this