Use iCloud Photos to store photos in iCloud
With iCloud Photos, all the photos and videos in your photo library are stored in iCloud, so you can access them from your Mac, PC, iOS devices, Apple TV and on iCloud.com.
Any new photos you add to Photos or take with an iOS device appear on all your devices that have iCloud Photos turned on. Your photos and albums are organised the same way on every device and if you make edits or remove items, you see the changes on all your devices.
Before you set up iCloud Photos, update to the latest version of macOS on your Mac or the latest version of iOS on your iOS device. See the Apple Support article Set up and use iCloud Photos.
Turn on iCloud Photos
If you’re not already signed in to iCloud, choose Apple menu 
> System Preferences, then click iCloud and sign in with your Apple ID and password.
In the Photos app
on your Mac, choose Photos > Preferences, then click iCloud.Select the iCloud Photos tick box.
Select one of the following options:
Download Originals to this Mac: Stores the full-size versions of your photos both on your Mac and in iCloud.
Optimise Mac Storage: Stores smaller versions of your photos on your Mac when storage space is limited and keeps the original, full-size photos in iCloud. Choose this option to conserve space on your Mac. To restore the originals to your Mac, just select “Download Originals to this Mac.”
Note: If this option is selected and you run low on storage space, only the still image of a Live Photo is stored on your Mac. When you open a Live Photo, the video portion is downloaded from iCloud so you can play it.
When you first turn on iCloud Photos, it can take a while to upload your photos to iCloud. You can continue to use Photos while your photos are being uploaded.
Tip: To temporarily pause uploading or downloading of photos and videos with iCloud Photos, click Photos in the sidebar, click Moments in the toolbar, then click the Pause button at the bottom of the Moments view. Photos pauses uploading and downloading for 24 hours and then resumes automatically.
iCloud Photos doesn’t store your projects or Smart Albums. To keep a backup of these items, make sure you back up the library to another storage device.
You can have multiple photo libraries, but iCloud Photos keeps only the photos and videos in the System Photo Library up to date. See System Photo Library overview and Designate a library as the System Photo Library.
Delete items from iCloud Photos
To delete an item from iCloud Photos, just delete it from your Photos library.
In the Photos app
on your Mac, select the items you want to delete, then press Delete.
Deleted photos and videos aren’t immediately removed from your library; they’re placed in the Recently Deleted album, where they remain for the number of days shown, and then are deleted. To remove the items immediately so that they’re no longer available on any device that uses iCloud Photos, see Delete photos or recover deleted ones in Photos.
Stop using iCloud Photos
Important: If you turn off iCloud Photos, you’ll be prompted to select “Download Originals to this Mac” in the iCloud pane of Photos preferences, so all your original photos can be downloaded from iCloud to your Mac. Be sure to allow time for your originals to download before turning off iCloud Photos.
In the Photos app
on your Mac, choose Photos > Preferences, then click iCloud.Deselect the iCloud Photos tick box.
If you want to turn off iCloud Photos on all your devices, open the iCloud pane of System Preferences, click the Manage button, click Photo Library, then click “Disable and delete.”
After you turn off iCloud Photos, edits you make to photos on your Mac don’t appear on your other devices and new photos you take aren’t added to Photos on your Mac. Your library remains in iCloud and available to other devices that use iCloud Photos.
WARNING: If you turn off iCloud Photos on all your devices, your photos and videos will be deleted from iCloud in 30 days and you won’t be able to recover them, unless you click Undo Delete before that time.