How do you add music to your youtube video

I want to add music

I suggest, if you're running Windows XP, use windows movie make. It should be already installed on your computer under programs.
just start the program, go and import the video, then import some music.
drag both of them to the timeline bar (at the bottom)
and then go to "Finish Movie"

If you can, get Adobe Premier, it essentially works the same way, but is a much better program