Assuming they have a voltage drop of 1.5v (there’s no datasheet for those for me to check but this should be the case for most) then the voltage after the LED should be about 3.5v. We want to limit the current to 20mA. What I’d suggest is pick up a big bundle of resistors from Radio Shack or Fry’s. Make sure they have about 220 Ohm, 330 Ohm, and 1k ohm resistors. Start with the 330 Ohm resistors first. If the bundles at radio shack or fry’s doesnt have these values (they are very common values) then just order a bunch online from newark.com, jameco.com or digikey.com. They’re damn cheap.
Run a wire to the VCC screw terminal on the Cthulhu. Solder 6 (or eight, one for each LED) wires onto the end of the VCC wire. Connect the positive leg of the LED to the wire, connect the resistor to the other leg of the LED, and connect the other leg of the resistors together and run a wire from the collection of resistor legs to ground.
If its too bright at 330 Ohm, try the 1k (it’ll be safer too since it uses less power). Try the 220 Ohm if you want brighter, but please try the 330 ohm first, Do NOT go less than the 220 Ohm!!
Yes, you want to wire them in parallel, using one resistor for each LED. Yes, there is a reason for this that’d take too much time to 'splain. Trust me.
For wattage, I’d say go with 1/4 watt. 1/2 watt works too. 1/8 watt could work, but I’d prefer you use 1/4 watt or larger.