Adding photos to Shared Album, using the web
Shared albums are not available to view on iCloud.com.  You can only create albums and add/delete photos in albums on a device and then share a link to them.

You'd have to share your album and send yourself a link in order to see in online.  

You can add/delete photos from any shared album while on your Mac.  After you do that, any subscribers to that album, Mac or PC, will be able to see the changes you made.

Add items to a shared album


In the Photos app  on your Mac, click a shared album under Shared in the sidebar.
Click “Add photos and videos.”
Select the photos, video clips, and Live Photos that you want, then click Add.
Subscribers to your shared album can play the video in the Live Photos. 


Remove items from a shared album


In the Photos app  on your Mac, click a shared album under Shared in the sidebar.
Select the items you want to remove, press Delete, then click Delete.
Photos removes the items from the shared album, but leaves the original items in your library.


Important: If you delete photos or videos that others added to the shared album, you won’t have copies of them in your library. If you want to keep these items, download them from the shared album before deleting them.

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