In a web browser, sign in to your Amazon account (providing your email address in the usual way);

Insert your Fido2 key into an available USB port,  then select the option "Security key";

Click , and you will prompted to enter the PIN code for your Fido key;

At the "Security key PIN" prompt, supply the PIN code for your Fido2 key, then click ;

You will now be asked to touch the Fido2 key (in the case of a Fido key with a fingerprint reader you will need to swipe your finger on the key);

Once the key has been touched you will be logged in to your Amazon account.