Press the up and down arrows simultaneously for 3 seconds and release. You will see F for Fahrenheit or C for Celcius on the screen. Either press the light button or wait 3 seconds and the screen will change to the first stage differential.The differential is adjustable with the arrows from .5-3 degrees in .5 degree increments. Press the light button or wait 3 seconds and the second stage differential will show.It is adjustable with the arrows from 1-6 degrees in .5 degree increments. Press the Light button or wait 3 seconds and the second stage delay will show. It  adjustable from 10-40 minutes in 5 minute increments. The thermostat will return to normal operation after a few seconds.