Thanks for the suggestions, using the details given and a bit of searching by you guys I managed to find what I was looking, so thank you!
I’m going to write the exact steps in case someone else needs this:
Dashboard -> Symbiostock Express-> Home Custom Carousel Settings -> Click on the slide that you want to modify, upload or choose the photo that you want as the category image, and then in the “Slide Link” tab paste the gallery link.
Now I just want to know how to add photos in the “Featured Images”, and maybe a drop down menu with the categories.