XF 1.3 How to change background to background image?


i have looked but havent found anything on this, i want to change my default blue background to an image ( ( image attached below )

I want to be able to do this without having to code anything

Thank you


As from what i have seen im starting to wonder if i can do it, i was not the one who installed the forum to the website so is this going to be a problem customising adding add ons?