software update
from version 10.12.6 to latest version 10.13.0 or higher
iMac 21.5", macOS 10.12
from version 10.12.6 to latest version 10.13.0 or higher
iMac 21.5", macOS 10.12
How to upgrade macOS to macOS 10.13 High Sierra
https://support.apple.com/en-us/HT208969
Ho to upgrade macOS to macOS 10.14 Mojave
https://support.apple.com/en-us/HT210190
How to upgrade to macOS Catalina
How to upgrade macOS to macOS 10.13 High Sierra
https://support.apple.com/en-us/HT208969
Ho to upgrade macOS to macOS 10.14 Mojave
https://support.apple.com/en-us/HT210190
How to upgrade to macOS Catalina
software update