Reset Theme

When I started my blog, I opted to not use images. I managed to delete that option somewhere along the lines and am trying to figure out how to get it back. I am wanting to have the image for each article like the demo shows. If I need to reset the theme, that is fine but I do not know how to without wiping my site. If you know how to add the photo option back in, that would be great. Thank you.

The page I need help with: [log in to see the link]