To add seasoning to popcorn made with an air popcorn popper maker, you can wait until the popcorn is done popping and transfer it to a large bowl. Then, drizzle some melted butter or oil over the popcorn and toss it well to coat. Finally, sprinkle your desired seasoning over the popcorn and toss again to ensure it is evenly distributed. Some popular seasoning options include salt, pepper, nutritional yeast, garlic powder, chili powder, or grated cheese.