Slide the system switch to the "Heat" or "Auto" setting and slide the fan switch to "Auto." This will disengage the whole house fan and allow the thermostat to regulate when the heater will turn on and off.
Press the "Warmer" key until the digital temperature display indicates a temperature at least 10 degrees Fahrenheit above the air temperature, and wait for the heater to kick on. Note that, depending on the heating system you use, there may be a delay before the heater turns on.
Slide the system switch to the "Cool" setting and repeat the same process, pressing the "Cooler" button until the thermostat temperature is at least 10 degrees Fahrenheit below the current air temperature. If your cooling system comes on at this point, you have successfully used the Honeywell T8600 to control your home heating and cooling system.