Well with Windows Movie Maker, you simply have to import a movie that's already on your hard drive, after its imported it should seperate into clips in the tray that says collections. Then you drag and drop to the storyboard. When your done editing your movie, you should be able to save it to your computer.
Now to upload a DVD on your computer you need a program. The one I'm using is called Magic DVD Ripper and you can download it free. It will convert your DVD into an AVI file.