How to import your Aperture library into Photos for OS X

[iMore.com]

If you're moving from Aperture to Photos for OS X, the first thing you'll need to do is import your library.
Apple's pulling the plug on future Aperture development. It still works with OS X Yosemite, but Photos for OS X is the future. Luckily, importing your existing Aperture library is easy. You can either do it during initial setup and make it your main Photos library, or you can import it at any time and make it an additional library. Once you've imported your library into Photos, you can still use the old version in Aperture. They won't stay in sync from that point on, but they will both remain accessible to their respective apps.

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