Figure: Form for adding a security key
First install any authenticator app, which supports the TOTP method, on your smartphone. Use this app to take a picture of the QR code displayed here or enter the security key into the app. A one-time password will then be displayed in the app, which you must enter in the field on this page. A new password appears in the app approximately every 30 seconds. With a click on Submit you will be redirected back to the page Two-factor authentication and the security key is displayed with its ID in the overview there.
Figure: Form for adding a security key