How to add a lightbox?
You can only have lightboxes in the Pro version of Smart Slider. There are two ways you can create lightboxes.
Lightbox from backgrounds
At your slider's settings -> Slides tab, you can turn on the Backgrounds in lightbox option.
This will create lightboxes from your Slide Background images.
Lightbox in links
within the Lightbox tab you can insert image urls or any other urls.