i have been looking for the same thing and i don't know what file to put it in or if it has to be a specific format or something like that but you can try Windows Live Movie Maker which is much easier to add music with but make sure all your editing information and video is imported to your pc and just put it into Movie Maker! When you put it in it just says what file did you download it in and browse it and find the music where you downloaded it! When you did that the music is added and no instruction is needed for editing music on that because it is fairly simple!
