Sign-in 2FA. Go to your Security settings. In the Sign-in Two-Factor Authentication (2FA) section, select Add passkey. When asked, insert your Hardware Security Key and follow the prompts. You can add up to five Passkeys.
Master Key. Go to your Security settings. Under Advanced Settings, select Enable next to Master Key, then choose Passkey (Recommended) and follow the prompts.
Funding 2FA. Go to your Security settings. Under Advanced Settings, select Enable next to Funding 2FA, then choose your YubiKey.
Add more than one 2FA method so you can still sign in if you lose one. See How to enable Multiple 2FA.