How do I enter the Installer Setup menu on the TH8320U?

From the home screen, press the System key, then press and hold the two blank touch keys on either side of the center blank key for approximately five seconds until the screen changes. The thermostat must be powered either with AAA alkaline batteries or with a 24 Vac Common wire before entering setup. The Installer Setup Number is displayed in the lower left as a four-digit code. (Page 9)