If you decide to do so, note that the RGB do have polarity, and the corner cutout on the LED needs to match the corner marked in black on the each of the LED footprints on the PCB. (See the picture below.) To solder the RGB LED, add a small amount of solder to one pad, place the LED onto the pads, and reheat the pad while stabilizing the LED with tweezers until a connection is made between the LED and the pad on the PCB. Now add a small amount of solder to the remaining 3 pads. I recommend using flux for this step.