Add photos to an iCloud Shared Photo Library on Mac
After you set up or join an iCloud Shared Photo Library in Photos, you can manually move photos and videos from your personal library to the shared library. Photos also suggests photos and videos you might want to move to the shared library.
You can also use settings on your iPhone or iPad to have photos and videos added to the shared library automatically when you take them.
Manually add photos and videos to the shared library
On your Mac, you can manually move photos or videos from your personal library to the shared library. The moved items then appear only in the shared library.
Go to the Photos app
on your Mac.Click the Library pop-up menu in the toolbar, then choose Personal Library.
Select the items you want to add to the shared library.
Choose Image > Move [number] Photos to Shared Library.
You can also Control-click one of the selected items, then choose Move [number] Photos to Shared Library.
To view the moved items, click the Library pop-up menu in the toolbar and choose Shared Library.
If you decide you want an item to appear in your personal library instead, you can move it back.
Add photos and videos with sharing suggestions
Sharing suggestions recommends photos you might want to add to your shared library, such as photos you took of participants of the shared library, photos you took when participants were nearby, or photos of people you indicated interest in during the setup process. Photos sends notifications to review sharing suggestions.
Go to the Photos app
on your Mac.Click the Library pop-up menu in the toolbar, then choose Both Libraries or Shared Library.
To view sharing suggestions, click For Your Shared Library in the sidebar.
Do one of the following:
Move a selection of items: Select the items you want added to the shared library, Control-click one of the items, then choose Move [number] Photos to Shared Library.
Move all suggested items: Click Move All to Shared Library at the top right.
To get sharing suggestions for additional people, choose Photos > Settings, click Shared Library, then click Add Other People. Select people you want to include in sharing suggestions, then click Add. To remove someone from sharing suggestions, hold the pointer over the person’s photo, then click 
.
To stop receiving sharing suggestions, choose Photos > Settings, click Shared Library, then deselect Shared Library Suggestions.
Add photos and videos directly from Camera
When you take photos and videos on your iPhone or iPad, you can set the Camera app to save the items to the shared library instead of your personal library. You can also choose to automatically add photos and videos when shared library participants are nearby, and automatically add photos and videos taken at home. For details, see Add content to an iCloud Shared Photo Library on iPhone.
If participants add exact duplicates when joining the shared library, the duplicates are merged automatically, and the Info window shows which participants added the item. See See who shared an item.