To mark something as a controlled substance, you open the gear menu and select "Inventory Settings".


Next you open the "Products and Services" section.


Enter some of the name of the inventory you are looking for (eg Tram for Tramadol).



Next click on the inventory you are looking for.


Here you have the ability to mark an item as a controlled substance specifically:

Check that option and save, and now VetBadger knows that this inventory item is a controlled substance.