When you log in for the first time to a Duo protected resource. Select Security Key from the list of devices and then click Continue.

Make sure that you're not blocking pop-up windows for the enrollment site before continuing.

If you're using Safari 14.1 or later, click the Initiate enrollment button to proceed. Other browsers do not require this step.

The security key enrollment window automatically tries to locate your connected security key for approval.

When enrolling your security key, you'll be prompted to tap to enroll your security key (possibly more than once). You may also be asked if you want to allow Duo to access information about your security key (click Allow or Proceed as applicable).

You'll see whether the security key identification was successful or not.

Congratulations! You have enrolled your security key.