You can install DutyList as an app straight from your browser.
Your browser may automatically invite you to install. Just accept the invitation.
If you didn't get the invitation, or you didn't accept it, you can still get the app. Open DutyList in your browser, go to your browser’s menu via the 3 dots or Safari's Share button and select the Install App or Add to Home Screen option.
Both ways the DutyList app is installed with an icon on your phone.