after a certain period of time has passed, a "?" will appear on the footprint screen. approximately 72 hours later (though this may vary due to factors such as GPS)
the footprints screen appears when you tap the name of a place in the upper left corner of the map.
you can add a spot from "?", and there are three main places.
🏡 your home
💻 your work
🎓 your school