To create a drop zone slideshow:
Make sure the menu that contains the drop zone you are adding a slideshow to is showing in the iDVD window.
Click the Media button, and then click the Photos button to access your photos.
Drag a photo album or folder onto a drop zone.
This automatically creates a drop zone slideshow. The first photo in the folder shows in the drop zone. If you do nothing else at this point, the slideshow “plays” the photos in the drop zone in the order they appear in the folder.
Click the drop zone.
The Photos pane (shown below) appears above the image.
Drag the slider in the Photos pane to change which image shows first in the drop zone.
Click the Edit Order button to change the order of images in the slideshow.
This opens the drop zone photo editor, which is similar to the slideshow editor but has fewer controls. You can drag the images into any order you want. You can also delete images by selecting them and pressing Delete. When you are done, click the Return button to go back to the drop zone editor.