how do I add thumbnails to the lightbox that opens after clicking on the woocomm

I don’t understand your question. What do you mean with “activate thumbnails when opening a lightbox”? PhotoSwipe itself has no thumbnails.

I was referring to the display of thumbnails. And also so that they are manageable and flip through the slide when clicked

Maybe there is a misunderstanding. PhotoSwipe does not provide any thumbnail view inside the lightbox. When you click an image, only that single image will be displayed and you can switch between the images by clicking the arrows or swiping the image.

Also see the examples here: https://wordpress-demo.arnowelzel.de/examples-lightbox-with-photoswipe/