After connecting your ecobee4 to Wi-Fi during the installation process the four digit registration code will be generated. The thermostat can be registered through the ecobee mobile app (iOS or Android) or the web portal, https://www.ecobee.com/register/.
If Wi-Fi set up or the registration was skipped during the installation, the registration code will be accessible through the Main Menu.
Tap the three horizontal bars in the bottom left hand corner to open the Main Menu.
A the top of the list, tap Registration. If it says "2 Steps Left" you will be directed to the Wi-Fi set-up and after its connected the code will be available. If it says "1 Step Left" it will show the registration code.
Once the thermostat has been registered, the Registration option will disapear from the Main Menu list.
If trying to add the thermostat to more than one device (ex. a second iPhone or Android), select "Log In" and use the email address and password set up when registered.
ecobee thermostats can only be registered to one email address at a time. If more than one user needs to connect to a thermostat, the email address and password need to be shared.