Those wires are for the the case power switch, and also the reset switch. The third one is probalby for power/hdd LED status lights. I've done a build with an Antec 900, but it's been awhile.......though I distinctly remember the switches are at the top.
Those wires plug into the "F-panel" spot on your motherboard. They let you turn the computer on and reset it. You need to check your motherboard manual to find out which wires go where........every mobo is slightly different. Your F-Panel on your mobo is located in the very bottom-left of the mobo itself according to the diagrams.......check page 2-33 in your mobo manual....top of the page, it shows you how to hook up those 2-pin wires.
Good luck!