image elargement

So I finally took the plunge and now I'm trying to create a site.  When someone navigates to my gallery (photography website btw) I would like for them to see thumbnails of the images and be able to click on one for larger view AND my caption (which is more of a mini story about the image).  The problem is the template for the layout of the gallery I want doesn't have enlargeable images, they are only the size at thumbnail.

Question: how do I change the template so I can have the images be a link to a larger version with caption?

The template I'm using is "Beaumont".

Thanks for any help you can give.