How do I wire a 4 wire RTD to a 3 wire input on a control?

You can connect a 4 wire RTD to a 3 wire instrument.  Just use 3 of the wires.  Generally a (4) wire RTD will have 2 white wires and 2 red wires.  The active element is between a red and a white wire.  The remainig wires are for lead wire resistance compensation. 
 
Red -------------|VVVVVVVVVVV|------------------------White
Red________|