your microswitch only has two positions: open and closed.
however there would be three connections for wires: common (ground), normally open, and normally closed. you only need 2 of them.
connect common to ground, and connect either normally open OR normally closed to a digital output. all that means is one connection will give you a binary high (until switch is pushed), and the other will always give a binary low (until switch is pushed). for a microcontroller it doesnt matter which one you choose.