Creating seperate main & page backgrounds

Hi, just wondering if you could give me some advice. (I am a newbie to Wordpress & Simple Catch Pro). On my blog I would like to create a patterned background (using an image) around the perimeter of the site with a white background behind the text similar to this blog www.abowlfulloflemons.net . At the moment the pink patterned background covers my whole site and the text is hard to read against it. I have been told that I am using the same image for the main background as I am for the page background. I can see where to change the page background but not sure where to make the changes to the main(perimeter) background. My blog is at www.homesweethomemaker.net . I hope my description makes sense :> Thank you in advance Sheree