Mac 
Get started with Photos for OS X
OS X Yosemite (v10.10.3) now includes the Photos app. If you were using iPhoto or Aperture, here’s more information about upgrading to Photos on your Mac.
If Photos won’t open a library that you already migrated
Photos lets you know if you try to open an iPhoto or Aperture library that you already migrated.
If Photos can’t copy or create a library
If the Photos app shows any of these alert messages when you first open Photos or migrate an existing iPhoto or Aperture library, follow these instructions.
If Photos can’t upgrade your library because it’s on an unsupported disk volume
Follow these steps if you see an “unsupported disk volume” error when you try to migrate an iPhoto or Aperture photo library to Photos.
How Photos displays Smart Albums from iPhoto or Aperture
Photos displays Smart Albums from iPhoto or Aperture based on the criteria you used to create them.
Use Photos and iCloud Photo Library on multiple Mac computers
Photos works with iCloud Photo Library so you can access your photos and videos on all your Mac computers.
Designate a System Photo Library in Photos
If you have multiple photo libraries on your Mac, you can choose one to be the System Photo Library. Apps like iMovie, Pages, and Keynote can use the images in the System Photo Library.
About the security content of OS X Yosemite v10.10.3 and Security Update 2015-004
This document describes the security content of OS X Yosemite v10.10.3 and Security Update 2015-004.
Adjust the size of your Photos library to work with iCloud Photo Library
If your Photos library is too large to work with iCloud Photo library, you can make some adjustments.
iMac (27-inch, Late 2012 and later): Installing or replacing memory
Learn how to install additional memory or replace the memory in your iMac (27-inch, Late 2012) and iMac (27-inch, Late 2013) computer.
