To activate Go Snapshot, you can open the camera or navigate to a specific Pokémon in your bag. Once you've picked the perfect spot and the Pokémon you want to take photos of/with, you tap the screen to toss their Poké Ball to that place. You'll then be able to move around the life-size Pokémon to find the best angles for your photos and even get it to turn around by brushing it to get its attention.
With Pokémon Go facing intense competition from other mobile games (in particular, Fortnite), not to mention the myriad other apps vying for our attention, adding fun updates such as Go Snapshot could help Niantic keep people coming back. Niantic says Go Snapshot will be available soon.