[SOLVED] How to upload my own background image?

Can someone remind me how to upload my own image to use as my background? I've done it once, but didn't like it so removed it and now I can't figure it out!

I've uploaded the image to: /wp-content/themes/atahualpa/images/image_name but I'm not sure what code to put into my settings. Can someone remind me please? I've inserted the following code, as indicated in the layout instructions, but is's still not working

background: url(/wp-content/themes/atahualpa/images/ChevronLtGrey.jpeg) repeat top left;

Thanks very much!