LED tail lights / Brake / Turn signals can be done by wiring the leds directly to your wiring coming to your tail light housing. However, one think you have to understand is, most cars recognize normal bulbs only, and if you hook leds ONLY to this wiring, certian cars will give you issues, such as not working or fast turn signals (like bulb burnt out). For Turn signals you 100% need to follow below:

Solution is to use LOAD LINE RESISTORS. What a Load line resitor is it fools the car in thinking that you still have normal bulbs hooked to the car. Since your trying to used LEDs you must place these resistors to the wiring. Please look below for the wiring. These resistors can be picked uped at any hobbie store, or Radio Shack, and the internet. You need at least 20Watt Resistors in 6ohm or 3 ohm depending on if your going to wiring LEDs in the Front and Rear of your turn signal.

You may not need to do this resistor modification if your only doing the brake/Tail light on certain cars. It depends on the car. But the Turn signal you must do on all cars!