Sign in to the your Logto account, then after clicking on your user icon select the option "Profile";

In the section "Account Settings", scroll down to the "Two-Factor Authentication" section, then against the option "Passkeys", click on the "Add" link;

A window will open titled "Create a passkey", click ;

You will now asked to specify where the passkey will be saved, select the option "Security key";

You will now be prompted to enter the PIN code for your Fido2 key.

At the prompt "Security Key PIN", enter the PIN code, then click . 

(in the case of a Fido key with a fingerprint reader you will need to swipe your finger on the key);

You are now prompted to touch the key (to prove you are present and giving permission for the key to be used).

Touch the necessary area on your Fido key;

Finally you are prompted to name the Fido2 key, enter a suitable name for your key then click ;

You passkey authentication method will now have been added as a logon option for Logto, and will show as a new passkey option in your account settings;