Download the yubikey authenticator app for macOS

Change the default PIN on a YubiKey

Plug in the device, and go to certificates.

You want to change the default pin code on the device, as it defaults to 123456 and you don’t want that in case someone finds your key. Once under certificates, go to Change Pin. Enter your pin values.

Change the PUK

Plug in the device, and go to certificates.

Once under certificates, go to Change PUK. Enter your PUK values.