Ok, then that makes it easy. There's a "like" option under every pic of your album. When you like them(even if they are from your own album) they'll be added to your favorites. Same thing happens when you like pics from someone else's album. Till now I haven't found an option to directly add a pic from a manga (while reading) to your favorites. May be other experienced member can shed more light on this matter.
so how do you do those include the pic in your favourites again?