This picture shows to position of motors and gearing for the drive and steering. The motor at the top of the picture is used for steering. It drives the two small bevel gears in the center of the robot which in turn spins the wheel modules simultaneously.
The motor towards the bottom of the picture is for the drive. As you see it is set up to drive the bevel gears at each end of the robot. Those bevel gears then drive down threw the wheel modules to power the wheels.