There will be a diode across the switch... test this first. Get your multi meter and set to CONTINUITY ( or beep if you have one)... put your probes on either side of the diode... if OK.. youll get very high reading ( high resistance) with probes one way... swap them over and you should get LOW reading ( or a beep if you have it).
If this tests OK.. then you need to put your RED lead on the side of the switch that has the diode end without the black band on it.. place BLACK lead on other side of switch and then press the switch... you should get a LOW reading to show good contact through the switch