Most times, you want to mount your PCB in a housing. To place the LED at your preferred position in the housing easily, you should solder the LED to some wires and the wires to you SHC PCB. Here's how to do this:

1. Cut the wires on the LED down to about 4mm.
2. Solder one wire of about 5cm to each of the pins.
3. Get about 10mm of heat shrink tube and place it over the soldering area.
4. Heat the tube shortly and carefully with the flame of a pocket lighter. It shrinks and should isolate the soldering area afterwards.
5. Solder the other end of the wires to your PCB. The + pin of the LED (which was the longer pin before you cut it) is the one which is connected to a small wire inside the LED and goes into the center of the LED.