Automation and Input Number

1 
I am trying to configure an automation to switch on a power switch when temperature is less than 19. 
![photo1|612x499](upload://dzQN4ZLOg8GZvKZnPwBqr1y2u6Z.jpeg)  
I use input_number where set this value. 
I don't know how to use it on automation.
Cloud you help me ?
Thanks
Stefano