Important: If you have not enrolled your YubiKey in Duo yet, please follow these instructions first:

Authenticating with your YubiKey

The next time you log in to Single Sign-On (SSO) application like Canvas or EagleNET, you can simply press/touch your YubiKey's gold-colored contact to log in when prompted to "Verify you identity". The experience shown below is in Chrome (recommended). 

If you cancel your browser's prompt to use the Yubikey or it times out as shown below, you can choose "Other options" to use another one of your 2nd factor methos.