So green I'm lost

I am relatively new to WP. Am using a Divi theme. Have set up a business website using Page Builder for all my pages. And, I don’t know HTML or coding (or CSS and whatever all that other stuff is).

I was advised by a friend who is a professional website builder that I need to switch the sliders on my website to something more like tiles. So, I was going to use a gallery or portfolio thing to accomplish that using my photos. I see “Portfolio” in my page builder, but when I add that to my page (in this case Home Page) I have no way to add the actual photos to it. I am stuck and don’t know what else to do.

My site is https://www.theallergyfriendlyvegetarian.com if you want to know what I’ve done so far. Thanks