Changing Theme Sidebar Image

I just started working on a blog https://www.birchwood-womens-health.com and am trying to change the background color on the right side bar and the right side bar image and can not find how to do this in the theme that was used to start the blog which is Atahualpa 3.6.7 Could someone direct me to which file I would find this information in for this theme. I would like to change the right side bar that is the leaf type design to the damask design I have the the tan color to a specified grey. Any help would be greatly appreciated.