Just use a standard Bosch-type automotive relay. There should be five terminals, labelled 85, 86, 87, 87a, and 30.
The easiest place to install the relay is behind the head unit.
Connect 85 to ground.
Connect 86 to the blue/white remote output from your deck.
Connect 87 to the red wire in your deck harness.
Connect 30 to the wire(s) that run to your amps' remote terminals. You can run a separate wire to each amp, or run a wire to the first amp, then connect a wire between that amp's remote terminal and the next amp, and so on.
Leave 87a disconnected.
The best way to attach wires to the relay's terminals are female, insulated 1/4" quick-disconnect terminals.
Dennis, the purpose of the relay is to avoid overloading the head unit's remote output with too much current.