To choose a theme:
Click the Themes button to access the Themes pane.
Choose a group of themes (for example, 7.0 themes) from the pop-up menu at the top of the Themes pane.
Choose All if you want to see all the available themes at once. Customized themes you have saved are listed under Favorites.
Click the triangle next to a theme master to see the family of different menu designs for the theme.
Click the thumbnail you want to use for the menu that is showing in the iDVD window.
After a short pause, the menu changes to the theme you selected.
You can apply any thumbnail to any type of menu. For example, you can apply the Chapters menu style of a theme to the main menu of your project.