To create a scene selection menu:
Make sure the menu or submenu to which you want to add the movie is showing in the iDVD window.
Drag a movie with chapter markers to the menu, being careful not to place it within a drop done.
iDVD automatically creates two buttons on the menu: a Play Movie button and a Scene Selection button that links to a scene selection menu. If the menu already has one or more buttons, iDVD instead creates a button with the title of the movie, which links to a submenu with Play Movie and Scene Selection buttons.
Double-click the Scene Selection button to open the scene selection menu, which has a button for each of the first several chapters in your movie.
The number of buttons displayed depends on the number of buttons the theme allows, up to 12. If you have more chapters in your movie, iDVD automatically creates additional scene selection menus to accommodate them.
The button labels (names) correspond to the chapter names you set in the video editing software; you can change them if you want. If your theme uses image buttons, the buttons contain thumbnails that match the first frame of each scene or chapter.
Click the Themes button, and if you want, choose a new theme for the scene selection menu, or customize the existing theme by changing the background image, the button style, and so on.
Each scene selection menu can have a different theme.