Do you have a youtube account already?
Open windows movie maker (it comes standard on most machines). On the tab at the top, click on "add videos and photos." Select the photo you want to use. After you pick the photo, you will be able to click on the "Add music" tab at the top. Pick the song from your pc. Save your video as a .wmv file. (i.e. myvideo.wmv). Then you just upload to youtube!