The ability to add Favorites come with level 2 currently.
Adding/Removing on Viewing Pages
When you are viewing a submission you can make it a Favorite by clicking on the blue "Add to Favorites" button under the stat column on the left side of the submission. Once you click it you will be taken back to the submission after a refresh and there will be an indicator underneath it showing that it is now in your Favorite's Stash.
You can favorite a sub as many times as you like and it will continue to appear for your sorting. Some may want the same sub in multiple lists which is why the Add button remains.
Now you will have the same "Add to Favorites" button but will also have a "In Favorites" notification with it. If you click that, it will take you to the Manage Favorites page.
If you just added a sub to your Favorites, It won't show up in any lists till you Manage your Favorites. Your new Favorite is currently in a slush pile on the Manage Favorites page awaiting your categorization. Use that "In Favorites" button to get there or choose it from the "Quick" dropdown menu up top.
Modifying your Favorites
When you first start choosing Favorites, nothing happens. They go into an empty category that doesn't show up anywhere. There is no default Favorite dump that will show up for anybody but you in the Manage Favorites page.
So go to the Favorites Editing page by going to "Organize Favorites" from the Quick dropdown main menu.
There you will see buttons to create your Favorite categories and how to organize them. There are some instructions there that will get you the rest of the way through managing your Favorites.
Once you have added favorites and categories your favorite list should show up in the right column area of the submissions you chose.
If anybody has Favorited that sub, there will be a link to see their full list.
If it is a sub you Favorited, you will see your list expanded allowing you to navigate to other favorites in that category.