How is operant conditioning applied in behavior modification?
The easiest example I could give you is training an animal (e.g. a dog).
You positively reinforce desired behavior (e.g. sitting) with treats.
Theoretically, you could reinforce the behavior by taking away a bad stimulus (negative reinforcement).
If the dog barks hysterically for seemingly no reason, you could negatively punish the dog by taking away a good stimulus (e.g. its comfy dog bed) or giving it a bad stimulus (yelling, dog whisperer style shh).