Can't get this javascript to work for the life of me. Please help.

Hey everyone, so I’m trying to get this script to work: https://www.dynamicdrive.com/dynamicindex14/fadeinslideshow.htm but having a lot of trouble.

I put the top code in the header.php

and the rest of the code in a text widget. What I’m trying to do is displaying a slideshow for advertisements.

My website is here:

https://joecrollard.com/portocall/#

As you can see, the only thing showing on the slideshow are the arrows.

Please help. Thanks!