Simple. If you amp has "high level" inputs you splice into the speaker wires and run them right into the amps high level inputs(L+,L-,R+,R-). If the amp does not have "high level" inputs you need to get a RCA line out convertor like a Scosche Loc80, seen below, splice into the speaker wires and hook them to the convertors high level inputs(L+,L-,R+,R-) then run RCAs from the convertor to the deck.