Help needed with tire pressure sensor's

I jsut installed my new tires/wheels and the tire pressure sensor  light is on called dealer and they said that I probably wouldn't be able to screw the sensor onto my new valve stems and I checked the TPS will not fir on my new valve stem. How can I get the light to go out and also how does a little threaded sleeve tell the truck if the tires are low. I unscrewed one and it's jsut a sleeve that threads onto the valve stem or did this guy tell me wrong?