Did you look at this video?
http://www.youtube.com/watch?v=GB_2x76tqnI
It is basically done like this (it has nothing to do with the cpanel):
1. go to acesitecreator.com, login, go to the members area on the right and download the color you would like.
2. open the file you downloaded. There will be an images folder
3. connect to your site via any FTP software. You will see the public_html folder. Inside of that, you will see the another images folder like the one you downloaded
4. upload the images folder you downloaded (overwriting the the one in your public html folder)
That's it. Please email if you have any problems.