How do I upgrade iPhoto to work with macOs?

Photos for Mac is the official successor to iPhoto since five years. When you launch Photos it will automatically open your last used iPhoto Library and you can access your photos again. If Photos cannot find your iPhoto Library, quit it again and hold down the options key ⌥ while launching Photos again. When the library chooser dialog appears, select the iPhoto Library.

Here is a user guide for Photos: Photos User Guide for Mac - Apple Support. Clich the "Table of Contents" link to see more.

No version of iPhoto will run in 10.15 or newer; it depends on a 32-bit library. Switch to Photos or a non-Apple product.

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