Displaying Galleries

I am trying to find a user friendly plugin that will allow me to view photos on a page that does not require advanced programming skills.
First off, how do you indicate what photos are part of a gallery?
Basically I want to post several photos on a page. When the user clicks on the first I want them to have the photo display in something like lightbox but have the ability to click a “next” button to advance to the next photo on the page.
The way it is now on my site I don’t get a “next” button coming up.

See below:
https://perfectstrangerstheband.com/?page_id=96

The way it displays is fine but there’s I need the next/back buttons.
Perhaps I am not indentifying a “gallery”?
If so how do I do this?