@chetww, thanks for reaching out. Have you connected your Iro to WiFi yet using the mobile app? Once your Iro is connected to the Rachio cloud (requires Blinkup via the mobile app), you can access the controller from your MacBook Air via the web app (no download required).
Please reference the install video or step by step guide if you have any questions. Feel free to reach out with any additional questions.
Hope this helps.