Wat style did you upload? Some of them need to be uploaded to the root directory and others require you to place them in images/styles/your style here...either way you must follow the directions for that style and not very off of it.
if youve got a problem knowing where to put the images, select the skin you want to use and right click to view source, and try to find an image thats being used by the skin and just copy the path.
