[SOLVED] How do I keep the background out of the content area?

I’m missing something.
How/where do I add a background image so that it's fixed and only in the background and not in the sidebar and content area?

This is the old template: http://southernmainetaekwondo.com/

This is the new template: http://www.barefootmarket.com/blog/

I need the marble from the old template to look the same in the new template. Usually I just add a line in the css, but this template seems to have an option for everything - which is good, I just can’t figure it out.

When I add the marble it goes across the entire post, in the content area, it doesn’t stay in the background.