YubiKey is a One-Time Password (OTP) generator in the form of a USB stick. When setting up 2FA choose the "YubiKey" option and enter your YubiKey token.
Every time you log it to your Coinfloor account you will need to provide a 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.