YubiKey is a One-Time Password (OTP) generator device in the form of a USB stick. Choose the "YubiKey" option and enter your YubiKey token. Every time you log it to your Coinfloor account you will need to provide the security token generated by your YubiKey.
Coinfloor supports 44-character YubiKey tokens. If you are a YubiKey VIP user, please use slot 2 to generate a valid token. FIDO U2F Security Key is not a compatible key. For more information visit the YubiKey FAQ