Scripting fatal errors?

[Rapsis]

Alright, now I'm trying to make a skybox, and oh boy am I pissed.
I've been trying to make one for around 4 or 5 hours I think; I have to figure everything out by myself because I can't find any USEFUL tutorials on the internet.
So, I have GIMP with the .dds plugin.
I can't find any single fucking skybox on the internet.
Some tutorials say "Download a .CUBEMAP file from this place, it's FREEEEEEEEEEEEEEEE!":
http://www.cgskies.com/sky.php?sky=338&t...&pagesize=

(I need daytime to add some contrast)
The fucking thing is, THERE IS NO .CUBEMAP FILE, JUST A DAMN JPG OR SOME SOME SHIT LIKE THAT.
Can any one explain this shit like you would explain it to a retard? I don't get this crap AT ALL.