On cars / motorbikes / trucks with European polarity (2 positive, 1 negative) nothing needs to be done. The diode can be used indifferently or not, because its effect will be zero.
If, on the other hand, the medium has reversed polarity (Japanese), with 2 negative and 1 positive instead, then simply insert the diode supplied into the special plug.
(It is recognized because it is the one with the largest electrical cables. The other plug that has thin electrical cables is used to drive the glare).
If inserting the diode the xenon kit does not work or does not dazzle correctly, remove the diode, rotate it 180 degrees, and reinsert it.