I also could not find anything for the ground wire install. How many wires do you have...4, 6, or 7?
It should have come with some kind of instructions...if not atleast where to place them. I have a few friends in my car club that have the ground wire kit on their mazda 3's. I will see if I can get some pics from them for you. I also plan on getting a ground wire system within the next month or so......so I also need to know the best place foir it.