Thanks! That encouraged me to poke around a little more. The changes are just more subtle than I expected.
Since then, I've been able to upload another couple of add ons, and seeing how they worked also helped.
OK - I've followed the instructions to upload and install this and. . . what next?
I didn't get any error messages and I see it in my Add Ons list.
But I don't see any way to purchase a license for it, or anything. The name is a link to a URL that goes to the main site for Hex Themes, but...