Apple released the update for Yosemite, 10.10.3, yesterday. You can get it through the Mac App Store if it doesn’t show up as an update or you can download the combo updater if you didn’t updated to 10.10.2.
With 10.10.3, comes the new Photos app. iMore.com has a good post about using Photos with multiple Macs. The post assumes that the different Macs are using the same iCloud account, however. If you are using different iCloud accounts on the different Macs, you would use the Shared tab and create a Shared Album.
