change Background to an image

Hello,

I have problem to set the background:
1. Which item in the styles are for the backgroound at the articel? Bcause they are always light gray
2. can I use a image for the background?

Thank you!

If you want to change the article background you have to customize the theme and add css code to your css/custom.css
www.joomlaplates.com/template-customizing

.main-outer {
background: #ff0000 !important;
}

www.w3schools.com/css/css_background.asp