With OS X El Capitan, Apple has added Extensions support for Photos, allowing you to add functionality to the photos app. You can apply edits from multiple extensions to one photo — or use any combination of extensions plus the editing tools built into Photos.
First install and enable extensions. You can find them at the Mac App Store by doing a search for Photos extensions. There are five currently available with prices ranging from US$1.99 to $14.99.
Next open System Preferences on your Mac and click Extensions. Click Photos in the left sidebar. Click the check boxes to enable the extensions you want to use in Photos.
To use an extension in Photos, double-click a photo in your library to open it in single view, then click Edit.
Click Extensions. You can find it at the bottom of the Photos editing tools on the right-hand side of the window.
OS X El Capitan is available as a free update from the Mac App Store. The operating system upgrade supports all Macs introduced in 2009 and later, and some models introduced in 2007 and 2008.