The deadringer layout does not show where to land the + side of the leds. Does it matter? Since the 3pdt is in control.
You'll want to add the current limiting resistor and LED off-board to the 9v supply of the DC jack. The other end hooks up to the 3PDT's as shown in the wiring diagram. I removed the on-board LED's in this version to make the board smaller (so it could fit in a 1590B). But, there's nothing special about how they are hooked up.