Burn an Auto-play DVD in iDVD

source: Burning a OneStep DVD from a folder in iDVD

You can skip the creative process completely and burn movies or other content directly from a folder on your hard disk to a DVD disc. When you insert the burned disc into a DVD player or a computer, the contents play automatically. This kind of disc is sometimes called “kiosk mode” and is a good way to create demos or other presentations that play automatically and require no user interaction.
You can create a OneStep DVD using a movie, video, or other files stored on a hard disk.
To burn a OneStep DVD from a folder:
Choose File > “OneStep DVD from Movie.”
Locate the movie you want to add in the dialog that opens, then click Import.
Insert a blank DVD disc into the optical drive.