Can't update from Sierra 10.12.6
Hi - I'm running a MacBook Air (13-inch, early 2015) and can't update it. It's currently Sierra 10.12.6 and when I try to update it it says "This update requires macOS version 10.13". I can't find a download for 10.13, only a supplemental update which I can't download either.
Can anyone provide me with the right download link - or offer any other assistance? Ultimately I want to run the newest OS.