Adding Yubico Key to MFA for PTS O365 Accounts
Navigate to myaccount.microsoft.com & sign in with your PTS email and password.
From the left side menu, click the disclosure triangle for “My Account”.
From the “My Account” options, please click on “Security Info”.
Under the sign in methods listed, please click on “+ Add sign-in method”.
A new menu will appear, from this menu please click on the “Passkey” option.
From the listing of options for a Passkey, please click “Next” 
You’ll then be brought to a “Setting up your passkey . . .” selection. Please click “Next”
You may be prompted to create a Passkey by other means, such as, FaceID or TouchID. Please click “Cancel”.
Once you’ve cancelled the alternative Passkey means, you’ll see another menu appear.
From this new menu, please select “USB security key”
Follow the on-screen prompts.
Insert your Yubico USB C Security key into a USB C port on your PTS-issued computer or via the connected docking station with an available USB port.
You’ll be prompted to create a 6-digit PIN for your Yubico USB C Security key.
**It is very important that you set this to something you will always know and will not forget as there is no way to reset this. **
You’ll then be prompted to press the button on the Yubico USB C Security key to approve the sign in.
Once you’ve successfully added the Yubico USB C Security key, you’ll be prompted to give it a name.
You’ll then receive a notice that the passkey has been successfully added to your account.