Using Multi-factor authentication with access.caltech

Login to access.caltech using your username and password as usual
When prompted for Multi-factor Authentication, click "Send me a Push" to use the smartphone app or click "Enter a passcode" to use your hardware token to approve your login
If you chose "Push", look for a prompt on your smartphone (if it doesn't appear immediately, open the Duo Mobile app) and press "Allow". If you chose "Passcode", make sure your Yubikey is inserted in a USB port on your computer and press the button on the key.