If you enable Geofencing on your phone then once you leave home with your phone, Away settings will kick in and temperatures will adjust according to your Away setup. You can remotely adjust the temperatures though if you think someone is at home. Note: ecobee doesn’t support geofencing on 2 phones. You will have to use HomeKit to enable geofencing on multiple phones.
And on the installation, follow below instructions. As long as you have all the necessary wires including C wire on your existing thermostat, it’s a simple process to replace it with new. See attached pictures for reference.
1. Shut off power to your thermostat and HVAC system at the circuit breaker.
2. If you have a separate turn on and off switch at HVAC switch board, turn it off as well.
3. Remove your original thermostat's faceplate.
4. Take a picture of your existing thermostat wiring.
5. Label your thermostat wires if they aren't already.
6. Disconnect your thermostat wires from your old thermostat.
7. Uninstall your original thermostat's baseplate.
8. Feed the wires through the new baseplate and screw it to the wall.
9. Connect the wires to the appropriate ports.
10. Attach the faceplate to the baseplate.
11. Turn power on to your HVAC system and thermostat at the circuit breaker and also at switch board.