When you run the wires for your lights, there will be supports between the plastic piece for the interior floor and the metal piece that mounts to the frame. The supports will have the center opened so you can run your wires, and out the hole in the bottom piece to your light housings. Simply mount the interior floor after you run the wires with double sided tape, which is included in the light kit, and your wires will be hidden.
Hope this helps, Big John