Use computer power supply for arcade

Hello,
I've removed a PC power supply to use to power my 60 in 1 multigame arcade cabinet. I've seen that a lot of people do this. Now that I've removed it I can see how it hooks to the circuit board and obviously it plugs into the outlet, but I can't figure out how to get it to power on nowthat it is removed? Any help would be greataly appreciated...