upgrade ios software

Unfortunately, you never said what you had, so there was no way to know or to refer you properly. Catalina is the latest version and there is no new OS to UPGRADE to. You may be able to UPDATE Catalina, however. To check, click on the Apple logo on the menu bar and go to About This Mac. In the window that will open you will see a report of what version you have. If it is 10.15.6, it is the most current version. If it is not, then down below is a button for Software Update. Click on it and it will start the update process. Side note: your system always knows what updates or upgrades it can accept.

Back up your data, check your applications for compatibility, and depending on which MacBook Air model you have, download El Capitan, High Sierra, or Catalina.

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