I have tried that and the parallax images does appear, but that's not what's meant to happen, the script should load the layers from the overlay folder automatically, meaning I should have a second layer appear above the ground layer which is some trees which are in file "para2-1" as seen in the screenshot I posted that shows contents of the overlay folder. Here's what the instructions included with the script say "
Create a folder and name it in Graphics Overlay.
Put all of your overlay into Graphics / Overlay.
Your overlay file will have the name: "Filename Prefix" + Map-ID + "-" + Number
Which "Filename Prefix" is the one you will config below
Map-ID is your map's ID
Number is 1, 2, 3, ... for using Overlay Variables.
Example: Graphics/Overlay/ground2-1.png
Which means this will be ground layer, for map 2, variable = 1
Light / Shadow must be. Jpg
Parallax / Ground must be. Png"
I don't see what I'm doing wrong as I'm pretty sure I've followed these instructions exactly, as the screenshots show the folders and me naming the files as the instruction say.