Tap on the settings icon on the iphone home screen. Scroll down till you see passwords and account.
Click on passwords and accounts.
Tap on add account. From the selection choose Exchange. Type your email address (firstname.lastname@example.org)
Select next in the top right corner. Choose Sign In. The NDUS system login will appear and type in your password.
Duo app will ask for approval. Once you approve Duo the account will be added.