Ground the negative lead, and probe the green wire on the TPS with the positive lead with the ignition in the ON position.
VAC is for AC voltage, like of that in the wall outlets of your home. VDC is for DC electricity, like in cars and such. Mostly anything that has a battery is DC but there are exceptions. Bat is to check the onboard batteries of your Multimeter. and OHM is to check the resistence of something, such as a resistor, heh. Hope that helps.
betwen orange and black you should see 5 volts plus or minus 0.5v, before you check the sensor. Between green and black you will see a voltage corresponding with throttle position. Should be 0.8-1 volt at closed throttle, and increase smoothly to greater than 4.5v at WOT.