Click on the 'i' bottom left corner of the iDVD window and you will see the dit functions.
A good guide to iDVD 7 can be found here:
Apple's tutorial on iDVD 07/08 is here:
Previewing before burning:
I've just tested placing a short (30 second) video clip into one of the Drop Zones on the Main Menu in the Reflection Black Theme. This worked perfectly.
I think your best course of action is to create a new Project in iMovie. Drag the 10 second segment from the Event clip to the Project. Now export the Project using Share > Media Browser, preferably choosing the Large size from the Apple presets. Given that DVDs are Standard Definition, there is little point in choosing the HD sizes (if available).
In iDVD, with your iDVD project open, drag the 10 second movie from the Media - Movies tab into the Drop Zone. The movie should now play inside that Drop Zone when you click on the "Start or stop motion" button just below the viewer.
Message was edited by: John Cogdell
Just having another look at it. If you click on the video in the Drop Zone inside the VIewer (not in the Drop Zone thumbnail box itself), a dotted line will appear around the video frame. Also, a slider bar will appear above the video allowing you to adjust the Start and End points. This suggests to me that you may be able to drag the full movie from the Media Browser into the Drop Zone, then adjust the Start and End points for the section you want to be visible.
(By full movie I mean the movie you are authoring and encoding for burning to a DVD - the one that you drag to the background of the Theme. I'm assuming, of course, that the segment you want for the Drop Zone is actually part of the movie you will be burning. If not, disregard this suggestion).