I want to replace my round manual HW t-stat, with new Prog HW RLV430A. The wires coming out of the old are red,yellow,green,white. The new only has 2 black wires. How do I combine all these? My furnace is propane forced air. Thanks!

Wrong thermostat for the application. The old stat was setup for heat and cool and it is a 24 volt unit. The new one is for 120/240 volts and is not designed to be used as a replacement for the one you have now.

http://customer.honeywell.com/techlit/pdf/69-0000s/69-1855.pdf