Super easy. They're essentially microorganisms that attack the specified insects. They come in a powder, which you need to refrigerate if you're not going to apply immediately. I'd recommend being home on the delivery date to receive and store appropriately. Mix the powder with water in a can (gently), and apply to the affected area. They'll stop the damage from spreading within a day or two.
Scooter mentioned Milky Spore, which is also effective, but can take several seasons to establish. Nematodes have immediate results and don't harm the environment.