Save photos in collection
There is also an option to Save or Bookmark your photos and keep it in your Favourites. If you want to save a particular photo, just open it and in the Details section you can see a Bookmark icon which you have to click to save the photo. In this way that photo gets saved in your online collection (Favorites).
There is an another way to save the photos and keep them in your Favorites as well. You just have to go the Photos home and hover to a photo that you want to save. You can see a Bookmark option in the top right corner, you just have to click on it and your photo will be saved.