Hello,
The url of the images is entered right into the module's backend. Edit the module in the module manager and on the right side of the edit screen you will see a section called Other Parameters. Under that section there are parameters for changing the image urls. For example:
Enter The URL Of The Image To Be Displayed In The Top Section When Hovering Over Box 1. Example:
http://www.shape5.com/picture.jpgThat parameter will change the top image when hovering over box 1.