How to add a lightbox on an Editor X templated product page?

Question:
[Because Lightboxes don’t have a link, how do I add a lightbox to all product pages and find a way to trigger it? ]

Product:
[Editor X.]

What are you trying to achieve:
[On a typical product page of any apparel websites, normally next to the size selection, there’s normally a link to a “size guide/size chart”. Then if you click it, a pop-up lightbox would appear showing a size chart. How do you do that on an Editor X product page? ]

What have you already tried:
[I was trying to add just a text link in the product description, then I found out that the text link has to link to an URL, but Lightbox doesn’t have a link, right?]