What color are the LEDs and how many are you trying to wire up?
Input voltage is between 12 and 14.4v, so I usually average it out to 13.8V for my calculations (conservative). You need to look at the spec of the LEDs to see with the forward voltage (Vf) is, which is usually around 2.2-3.5v. Then there's the driving current which ranges from 20-70mA. From there you'll be able to calculate the required current limiting resistor.
Look up online for LEDs and calculators.
Piranha LEDs are 4 terminal, each pair on one side are of the same polarity. These LEDs have 4 terminals for improved mechanical stability on PCBs.
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