content box

Hello,

I am still new to drupal so be gentle, lol. I recently downloaded burnt rubber theme and have been editing it to fit my needs. However, currently i am trying to edit the content box (i believe that is the title of it) to use a background image (a closed box) for each new post, but i cant seem to find the css information to allow me to edit this setting in the current theme.

Thank you for any help that you could provide