I have this head unit: Kenwood KDC-MP438U(http://www.crutchfield.com/S-Og2xRkCmnLS/p_113MP438U/Kenwood-KDC-MP438U.html)

and these speakers: Kenwood KFC-1661S(http://www.crutchfield.com/p_113KFC1661/Kenwood-KFC-1661S.html?tp=95)

I recently bought the SPX Audio 1000W Sub Box w/ Amplifier(http://spoofriday.com/SPX-Audio-100W-Sub-Box-w-Amplifier-at-PepBoys) and it comes with the wiring kit, but I dont know how to install it or if I should hook it up just to the amps or to the speakers too... can anybody help me out?