lucy24 - 9:48 am on Jul 10, 2013 (gmt 0)
I can't locate the html that puts the image on the page.
Have you got the html open in some type of editor? Search for the string
If it's an ordinary image displayed in the ordinary way-- not yet a background, the way you want it to be-- it has to turn up. Probably very near the beginning of the file. That is, ahem, shortly after the word <body>. I don't know how much clutter is in the <head> so far.
It would be easier to answer if we all had a clearer idea what your current knowledge level is. If you're helplessly staring at a wad of HTML feeling like a monkey looking at the innards of a Swiss watch, that would need one type of answer. If you're accustomed to HTML and CSS but have never happened to do a background image before, that's a different type of answer.
Bite your tongue :-P