Log in to your account. Click on "trigger events" in the menu. Click on "+ create new event". Choose a name for the event and click on "create". Your event is now created in the list. Drag the engine heater icon to triggers. Select departure time. Choose which thermometer you want to read the outdoor temperature (if you have several). Below actions in the same event, pull up the unit to which your engine heater is connected.
(All the steps need to be done in the desktop)