Add photos and videos to Favourites on iCloud.com
When you add a photo or video to Favourites in Photos on iCloud.com, it’s added to Favourites on any device with iCloud Photos turned on.
In Photos on iCloud.com, tap the Photos tab and then tap Select.
Tap the photos or videos you want to mark a favourite, then tap at the top of the window.
To see your Favourites, tap the Albums tab and then tap Favourites in the All Photos & Favourites section.
If you want to remove a photo or video from Favourites, tap the photo or video and then tap the Favourites icon at the top of the window to de-select it. If you delete a photo or video from Favourites, it’s deleted from all your devices with iCloud Photos turned on.