How do I turn on two-factor sign-in?

Security & Privacy → Two-factor authentication. You'll need an authenticator app.

  1. Go to Account Dashboard → Security & Privacy → Sign-in.
  2. Turn on Two-factor authentication. Enter your account PIN if asked.
  3. Enter your password, scan the setup code with an authenticator app, and type the 6-digit code it shows.
  4. Save your 8 backup codes somewhere safe. Each one works once if you lose your phone.

From then on, Log In asks for a code from the app on every new sign-in. To turn it off, use the same switch, with your password and a code.