ImageBg Step by step tutorial

Hi
I know that this topic has been spoken about before, but I am still totally lost....
The frontpage can contain big header image if you add in the template settings (on the "Features" tab the imageBg page suffix.

What I need is a step by step guide am I'm sure it would be pretty useful to have:
1. I have changed the demo pic to my own using FTP now what...
2. How does the page suffix module work on the features tab...It seems to make no difference what rules I add..

Any help is welcome!!!

I dont quite understand what You are trying to do. If You replace demo image by any other - it should work out of the box.
Please provide url to Your site and a little more precise description of things You would like to do.