The information is indicative and the threshold voltage of the LEDs may vary.
If you don’t want to fiddle with resistors, order a constant current LED driver at the same time, or for a 1 watt LED a handy 6-12 volt constant current driver.

Power responses can be ordered here.
Operating voltage Threshold voltage 3.5 V Threshold voltage 2.1 V
5 V 4.3 ohm 8.3 ohm
6 V 7.2 ohm 11 ohm
8 V 13 ohms 17 ohms
9 V 16 ohms 20 ohms
10 V 19 ohms 23 ohms
12 V 24 ohms 28 ohms
12.5 V 26 ohms 30 ohms
13.8 V 30 ohm 33 ohm
24 V 59 ohms 63 ohms

This table gives a power output of approx. 350 mA current. The resistance value is indicative, choose the closest resistance value and always preferably upwards, so as not to exceed the current rating of the LED. If you want to get the optimum output from your LED safely, choose the led-driver. For operating voltages above 15 volts, the resistor should preferably be rated at 9 W, below 15 volts at 5 W.

The required power dissipation (P) of the resistors can be calculated from the formula P=UI, where U= voltage to be dissipated and I= current through the LED (here usually 0.35A).

The resistors get hot, so don’t plug them into the cooling fin of the power diodes, the power diodes will heat up enough as it is.