Wiring Switches and LEDs on Flightsim Panels

I know this is going to sound lame but I have a new B737 Engine/APU Fire Control panel. The panel has a number of switches and LEDs. Each component has 3 lugs. I'm wiring the panel components to a master I/O control card which has sets of pins for Inputs and Outputs. Each set has a common (or ground) wire.

My question - how do you connect wires from the components to the board. Which (switch/LED) terminal is ground, do you use all three lugs, or do you just use one lug plus the "ground" lug, etc. I've looked on the Internet but cannot find any info for wiring these types of components.

Can someone please help.

Thanks

Frank