To prevent the front wheels from falling off, use the short zip ties to tighten the wheels onto the motors. If you find that the wheels still fall off, remove the wheels, place hot glue into  the hole and reattach them.

Plug in the motor shield and wire up the two motors:

Attach Sensor holders:

If the sensor holders a loose, use small zip ties to attach them to the motors.

Attach the sensor PCB:

Attach the battery pack (with the 6 AA batteries inserted) using the two large zip ties. One will need to go in from the top and the other from the bottom before you join them together:

Each kit needs 3 wheels, two of which need to have their hub enlarged to 5mm. This can be done very easily on a drill press running on a slow speed or by hand with a drill bit.