First, have a look at the
RC specs especially regarding the relay outputs, then have a look at the
spike specs, taking note of the two solenoid example.
Give it a bit of thought and you'll figure out how to drive an LED off the 5 volts that comes out of the FWD and REV pins of the Relay outputs, with the black wire being Ground/Negative/Cathode. Do not forget the dropping resistor.
Alternative would be to use a spike, since then you could drive 20 Amps of lights, but the RC can drive an LED at perhaps 10 mA
Have fun,
Don