I'm working on a short film that I plan on shooting on Super 8, silent, 18 fps. I'll edit the film, but then what? What are my options?

What I want to do is add sound to the film. It's a silent film, but I want to have a musical score playing throughout, to add some mood to the action on screen.

If I transfer my film to DVD, can I then use my computer to add a separate soundtrack to it (music, not dialogue), and then copy it onto a DVD disc (where it would now have sound as opposed to the original disc which was silent)?