Bumping an old thread here...but I'm having issues installing my HIDs into my foglights.

If I understand correctly, the positive spade goes into the original connector, but what I don't understand how the negative wire will be grounded to the headlight? I see the wire that is grounded to the headlight from the factory, but I don't understand how I could ground the aftermarket neg spade to the same sopt. Can somebody explain? I'm really trying to not to have to tap the neg wire into another if possible.