1. Navigate to here.
https://myaccount.google.com/signinoptions/twosv

2. Under Second steps, click on "Passkeys and security keys".

 

3. Click on "Use a security key".

4. Click on "Security Key" then click "Next".

5. Click "OK".

6. Click "OK".

 

7. Insert your Yubico key into the USB port of the Computer/Chromebook. Once completed touch the Yubico key.

8. Click on "OK". The Yubico key has now been added to your Google account. You will now get prompted with the below message, click on "Continue".

9. This will return you to the page found here. Click on "Turn on 2-Step Verification" 

10. Click "Done". 

Your Yubico key has now been successfully added to your account and you have now enabled 2FA for your Google account.