In a drag drop question the student must use the mouse to drag and drop one or more images on special rectangular areas (hotspots of another image (background)
You must define at least the image to be used as backgound and at least one other image to drag and drop
Don't use the imput fields to define image and hotspots coordinates. You will define them graphically with the mouse in the second step
For each image you can optionnaly enter in the "Text" field some text that will be shown under the initial position of the drag and drop image during the question attempt.
For a basic usage where each image has only one coprresponding hospot in wich it should be droppen, you can ignore the "Alernative Hotspots" field.
Additional help can be found in this tutorial.