how do i download the new mac os in a old imac
how do install mac os catalina to a old 10.11.6 mac
Back up your data, check your applications for compatibility, click here, and if the Mac is a 2012 or newer model(2013 for desktop Mac Pros), then on the download link for Catalina.
Catalina and newer won't run 32-bit software; download and use Go64 as well as using the first link above.
(230037)