If you look at the plugin’s readme doc and scroll down to where it talks about shortcode usage, you’ll see an example that does something like this:
[icon name="stroopwafel" prefix="fal"]
That prefix attribute is the one you’d change to use the various prefixes corresponding to the different styles. This example uses prefix “fal” for the “Light” style.
You’ll find all of those prefix/style options in the icon gallery. Find an icon you like. Click it to see its detail. On the right, select the style you prefer. You’ll then see the prefix noted in the detail at the top of that icon’s detail view for that particular style.
Have fun!
