Turn on heating with sonoff temperature sensor

Hi all

I have managed to integrate my nest and my sonoff temperature sensors. I want to be able to say if either of my 2 temperature sensors drop below 16c set temp to 18c

I know how to call the nest to set it I just can’t figure out the triggers in the automation

The sensors are showing as entities which I can select but not sure the right format to use on the trigger.

Help appreciated

Thanks