Trying to set up a Lightbox, gen project questions

So I am trying to set up a lightbox under “my work” and then “graphic design”, but it’s not working. I think it’s an issue with the onclick. Any advice?

Also, if anyone has any advice for anything let me know! Some pages are just placeholders right now until I get them set up.

There’s a W3school tutorial on that:

That’s actually where I got all of my code! The only thing I changed was the image source and it’s still not working