With DCC, add a resistor to the LED circuit since LEDs are a set voltage. Red and green are about 1.5 V and white and blue up to about 3.3V. You need to know about what voltage is on the track to calculate. You also need to put the light circuit parallel with and not in series with the track, not enough current can pass through the LED to run a locomotive. Ask if you need more help, it's not hard but if you've never done it before....