Duo - Install Mobile App

On your smartphone, search for the Duo Mobile app in your app store. Make sure the manufacturer is Duo Security, Inc., and then click Install.

Install Duo AppiOS App Store
 
Once installed, click Open.

Open Duo Mobile App

You will be prompted to enable "Push" notifications and to enable access to your phone's camera. You need to click on OK for both.

iOS Enable Push NotificationsiOSEnableCameraAccess