To set your configuration code you must first go the Online Install Guide at www.zenthermostat.com/install to identify your existing heating and cooling system's wiring and thus determine your configuration code.
Once you know your code, pull your ZEN display from the wall and press the CONFIG button on the rear of the display. The display will change to say “CONF” and you can input your configuration code by using the up or down arrows. Once you have set your code, center-touch the display to lock in the configuration. The code will flash once to confirm your selection.