I'm new and need to know how to customize background
 

I want to change the background color of my page (what's behind the forum style template) and also just how to add a graphic at the top. I've read the manual, but still can't find the file I need to edit. I know HTML and some CSS, so I can do it, but which file do I tweak? Please help. Thanks so much

See these pages in the manual - they should help with figuring out which CSS you need to change - Color Map Reference

The graphic at the top is usually the header template.

Thank you. I'll check it out.

--------------- Added [DATE]1222792460[/DATE] at [TIME]1222792460[/TIME] ---------------

Ok. I looked and I understand the references in the Manual. But I still can't figure out what FILE I edit and where to find it. Thanks again.

I think your looking for images/misc/vbulletin3_logo_white.gif, thats the default file location for the "banner". If you have a skin, it could be anything.

Here is part of the default header template:
$stylevar[titleimage] is defined in Style Manager > find your style > StyleVars > Title Image