HTML Coding for Wordpress Website

I am looking for some basic code that can be added to a small section of my website.

Currently I have a thumbnail image that when I hover my mouse over, the image changes to another, and then when the mouse is moved off, it returns back to the original image.

I would like the user to then be able to click on the image also for it to open as a Pop-Up Lightbox (or similar) so the User can see an enlarged version of the image(s) with some caption to provide them with further detail.

I need it that I can simply update with the image location should I need to change the image (or duplicate) the coding onto another page.