What they doEdit
Each OP when applied to a plot or processor causes it to go through one operation automatically without needing to have anything clicked.
How to get themEdit
Where they showEdit
Overlaying the bottom-left corner of your ranch image is a two-cogwheel icon with your current tally of unused OP. Normally it is accompanied by the words "show automation" if you hover over it. Click on it and it will change to "hide automation" while every processor displays a button saying "ON" or "OFF".
Hover over one of your plots or processors to see whether it says "Automation ON".
How to use themEdit
Click the bottom-left icon to display the ON or OFF buttons on the processors.
Click any OFF button to change it to ON; that processor will then start working automatically whenever there are suitable products in the barn and any spare OP.