You're probably trying to move it to /usr/share/fluxbox/backgrounds, yes? This is not writeable by regular users. It would be much easier to put the image in your own .fluxbox/backgrounds directory instead. Not only is it writeable by you without any extra work, but it is also easier to back up.
As a fairly common practice, if you have a choice between editing personal files or system files in order to accomplish the same task, you should usually stick with personal files (unless you want to make a change that has to affect every user). Mistakes made to personal files are easily corrected by falling back to the defauls. Mistakes made to system files are system-wide mistakes.i dont have a home/dsl/flubox/backrounds folder i am soo lost can somone give me step by step instructions?You at least have a /home/dsl/.fluxbox directory, unless you've deleted it yourself. It is a hidden file (note the dot in ".fluxbox"), so you'll need to toggle hidden if you want to get to it through emelfm (click the "H" button or press ctrl+h). If there's no backgrounds directory in .fluxbox, just create one and you're good.