You can launch Firefly by holding down the side button, or launch it from the Carousel or App Grid. The main screen kind of looks like the Camera app, but you’ll see little points of light hovering around—you know, like fireflies. Then you just point your phone at something, like a sign, product packaging, a book or CD cover, a movie poster, a barcode, a business card, and so on. If Firefly can identify it, it will do so pretty quickly, but it stays in scanning mode. You have to tap on a result to see more details, or swipe up to access the full list of everything you’ve identified.
Firefly does make mistakes—if misidentifies the front of a package, try again with the barcode. But generic or store-brand food packaging is particularly tricky, for example, since Amazon isn’t likely to sell that exact item.