Photos—formerly iPhoto—is macOS’s default app for organizing photos. Photos integrates with iCloud and keeps everything synced across your devices. It does a lot of the work on its own and keeps your library reasonably tidy without you having to do much, but it also has support for user-made albums and other organizational features.
Setting Up and Importing Your Photos
When you open up the app for the first time, you’re asked if you want to link you iCloud. If you do, go ahead and click the “Use iCloud Photos” button. If now, click the “Not Now” link. You can always set it up later if you don’t want to do it right away.
After that, you’ll find yourself in the main Photos window. If you have other pictures you want to import into Photos, select File > Import or press Shift+Command+I to open the import window. You can import photos by dragging them from Finder, pulling them from a camera, or selecting a folder and then choosing the pictures to import.
Here, we’ve selected a folder from which to import. Once you select your folder, hit the “Review For Import” button.
Next, you can review the pictures you want to import. If you want to import all the pictures in the folder, go ahead and click the “Import All New Photos” button. Otherwise, you can select just the images you want to import and then click the “Import Selected” button. By default, images are just imported to your Library, but you can also import them to a new album if you want to stay a little more organized. It will still add all the photos to your main photo library.
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Source: How-To Geek