Duo - Using SMS/Text To Authenticate
Now that you have SMS/Text setup you can use it by following the instructions in this article to authenticate.
After logging into an application protected by Duo, make sure the correct Device is selected then click Enter A Passcode (if you never setup Duo Mobile on the device the Duo Push option will not be listed like it is below).

Click Text Me new codes then enter the code and click Log In

For further assistance please contact the Eagle Help Desk at x8774.