There are two ways to add an image to your favorites... one way is to click the little star icon to the right of the image you want to add...see image below
(http://www.thefantasiesattic.net/images/tuts/add2fave/add2fave1.jpg)
OR the second way is the link directly above the comment section as shown below:
(http://www.thefantasiesattic.net/images/tuts/add2fave/add2fave2.jpg)
Once you do that it will return you to the "Home" page of the gallery with a message that it was a Success.