i have os x yosemite 10.10.5, how do i update this, the appstore tells me there are no updates other that for photos

Back up your data, check the application compatibility table, click here, and then on the download link for a more-recent OS. A Mac running Yosemite can be upgraded at least as far as El Capitan.

Catalina and higher won't run 32-bit software; if you upgrade to one of them, use Go64 as well.

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