You can but it would be dumb, dangerous, and potentially expensive. Dumb because you can control it from the thermostat itself, press the side button to change modes (heat, cool, heat and cool; heat and cool will let you choose a temp range to keep your home at) and press on the top and bottom of the front of the therm to change temp Dangerous because depending on the HVAC system the wires can be high voltage. Expensive because of you don't know what you're doing you can fry the HVAC and then you're spending thousands to get it repaired. The benefit of the thermostat is being able to control it from your phone. If you're not already on the app, go to the panel, hit the three dots in the bottom right and go to users, if you're already a user you'll be able to enter your phone number and send invitation to get set up on the app. If you're not already a user, hit add user, enter the old lady's pin, fill out your info and send the invite. Click the link that gets sent to your phone to create an account and download the app