How to upload backgrounds?

I’m new to Gmod.Org, and I’m wondering:
How to upload Backgrounds?

It says no screenshots or non-zip files, and I don’t know how to change either one.

DO NOT upload backgrounds, nobody wants them.

Oh

Nevermind then

No,Just No

You don’t.

Let us see an image of it . If it is decent i’ll show you how to do it .