In order to enable 2FA in your Nexex account, do as follows:
go to your Account page - Security - Two Factor Authentication or click here
backup or write down your Security Key (it is mandatory to retrieve your 2FA code in case you lose or break your device)
scan the given QR code with your device
enter the displayed 6 digits code in the Authentication code field
Please notice that 2FA codes change every 30 seconds. If during the login process the 6 digits code shows as wrong, try again with the new displayed code.