For appointments held at a client's home, checking in and out keeps you watched while you're alone with a client — silence itself raises the alarm, so you never have to reach for your phone to call for help.
In the instructor portal, go to My Profile and scroll to "Emergency contact" at the bottom of the form. Enter a name, phone number, and relationship. It's optional, but strongly recommended before your first home visit — it's the one thing your studio uses to reach someone if you're ever overdue checking out. It's never shown to members and never appears on your public profile; only your studio sees it, and only if a visit goes overdue.
On My Appointments, any appointment held at a client's home shows a "Check in" button — appointments elsewhere don't have one. Tap it when you arrive. This starts the safety watch for that visit: from here, the system is tracking whether you check out on time.
When you're done and heading out, tap "Check out" on the same appointment. This is the only thing that ends the watch. Marking the appointment "Complete" does not check you out — those are two separate buttons for two separate things, and forgetting to tap Check out leaves the alert clock running even after the session is finished.
If you're not sure whether you already checked in or out, tap the button again — it won't move the recorded time or cause any duplicate action.