How do I start using an authenticator app?

Using it is very simple:

  1. if you haven't already got it, you'll need to download the app
  2. go to your settings and enable 2-Factor Authentication (2FA), and
  3. once it’s enabled, the service will ask you to take a snapshot of a QR code using the app

Android users: if you're using Google's Authenticator app and you haven't already got a QR code reader, you'll need one of these to get set up).