On Engine DDI page (SUPT/ENG) you will find "INLET TEMP" row indicating temperature at engine intake. While you are airborne and your pitot heat switch is in AUTO position, pitot, static and AoA probes heating will be automatically on, unless there is a malfuncion of WoW system. For engine heat, as Foka said, you do not need to put it on unless you receive INLET ICE caution or you are about to climb through icing conditions.