Want to rock a photo from your library on your desktop? Photos for OS X makes it easy.
Photos for OS X may look very different from Aperture or iPhoto, but it still offers many of the same features — including a quick way to set a photo as your desktop picture. It's great for those moments when you come across the perfect picture and instantly know you want it as your wallpaper.
Setting your desktop is as simple as selecting the photo you want to use and clicking the Share button in the toolbar, then selecting the "Set Desktop Picture" option.
Once you've set your desktop, you can adjust its fill by going to the Apple menu and selecting System Preferences > Desktop & Screen Saver.