Slideshow Post Type

I am using a cherry framework portfolio section.
I am following these instructions to make a slideshow type.
https://www.templatemonster.com/help/wordpres-how-to-create-portfolio-galleryslider-post.html?_ga=1.267166094.1022835183.1458672181

For some reason, it says, that you need to UPLOAD the image on that page itself, select them, and hit insert.
Then you are supposed to delete them from the content box, and hit publish.

It sounds so backwards, but it does work.

The only problem I have, is if I let’s say upload 5 images and then I need to make a change, like remove one of them, I need to re-upload the 4 images again.
This is especially troublesome, when I hand it over to my client and they don’t have all those original images.

There must be a better way to do this.