To set which part of a movie plays in a drop zone:
From the menu (not from the drop zone editor), select the drop zone you have added a movie to.
When it is selected, a black and yellow line appears around the drop zone, and the Movie slider (shown below) appears.
Drag each of the sliders to specify where you want the movie to begin and end.
As you drag, the movie plays in the drop zone. Click outside of the drop zone to exit edit mode.
To see how the movie looks, click the Motion button (shown below). Click the button again to stop the motion.