Simply view the deviation which you wish to add and click the "Add to Favourites" button located to the right of the deviation. The deviation will then be added to your favourites.
To remove a favourite, view the deviation again and click on the "Remove Favourite" link located to the right of the deviation. The deviation will then be removed from your favourites.
Another way to remove a deviation you have added to a favourite is to simply hover over the thumbnail. If the deviation is in your favourites and you hover over a thumbnail, anywhere on site, a green/black Star icon will appear in the upper right corner.
If you then hover over that green/black Star icon, it will turn to an "x" and, when clicked, the deviation will be removed from your favourites. A notification will appear at the very bottom of the web page confirming it has been removed.
Finally, you can delete favourites from the Favourites Tab itself by entering Edit Mode. Simply select the "Edit Page" button near the top right of the page.
An "Edit Your Gallery" banner will then appear near the top of the page. You can then click the Edit Pencil icon that appears next to each deviation when you hover over it. There will be an option to "Remove from Favourites."
Once you have finished editing, you can click the blue "Done" button near the top of the page to set the changes.