If you haven’t already, download the Nest app on a phone or tablet.
On the Nest app home screen, tap the Settings cog.
Tap Add product. The app will switch to a camera view to scan the thermostat’s QR code.
On the thermostat, press it to open the quick view menu and tap the Settings cog.
Turn the ring to select Nest app and press to open it.
Select QR code. Your thermostat will show you a unique QR code to scan with the app. If it doesn't, tap Continuewithoutscanning in the app and select Getentrykey on your thermostat instead.