If you have not yet activated your card, you will be prompted to enter information that your card provider will use to confirm your identity. Your information will be validated immediately by your card provider and then you will be prompted to create a password to activate the service. Once activated, your Mastercard card number cannot be used without your personal password for online purchases with online retailers participating in Mastercard SecureCode. If you have already activated your card, after you enter your card number during checkout and submit your order, a Mastercard SecureCode window will appear and your card provider will display an authentication page. Enter your username and password and click submit. Once your identity is verified by your card provider, your checkout continues.