To use Duo Push, install the Duo Mobile app from the App Store or Google Play. During setup, a QR code will be shown. Open Duo Mobile, tap "Add" and scan the code. If you are already on your phone, you can simply follow the provided link instead.
After setup, each login works the same way: enter your username and password, then approve the push notification in Duo Mobile. If your organization uses Verified Duo Push, enter the three-digit code displayed on the login screen before approving.
Your phone must be online (Wi-Fi or mobile data) to receive pushes. If a push does not arrive, you can generate and use a passcode in Duo Mobile (if enabled).