Turning it on takes a couple of taps, as long as your account qualifies.
- Make sure you are Trainer level 20 or higher. Below that, the gadget is not offered.
- On the map, look for the Explorer Gadget icon in the top right corner and tap it. If it is not there, open your Item Bag and check the Key Items section.
- Switch it on. You can keep playing, or lock your phone and carry it with you.
- Walk at a casual pace. It is built for walking, so moving fast is not the way to get results.
- Tap the gadget icon again any time to see a summary of the Pokémon it caught, how many it caught and how many PokéStops it spun.
Keep some space free. If your Pokémon storage fills up, it stops catching, and if your Item Bag is full, it stops spinning PokéStops.
How to take over a catch yourself
Spot a pink Poké Ball over a Pokémon you would rather catch by hand, perhaps a shiny candidate or one you want to throw a curveball at? Tap that Pokémon or PokéStop yourself and you take over from the gadget.
Be quick about it. Scopely says you only get a limited window after the pink icon appears, though it has not said how many seconds that window lasts.