I actually figured this out, after sorting through the back-end UI. Anyway, for those who had the same question:
Go to Table VI B 2. Thumbnail Link. Set this to “lightbox.”
You’ll get an error saying something like “need to turn off pop over…”
Go to Table IV C 8. Thumb Popup. Un-check this box and the lightbox will work.
This is a great plugin; however, the back-end UI could use some work, but does offer a lot of features once you sort though them.