First, make sure you have Avatar Builder Girls or Guys Edition installed on your BlackBerry. Head on over to BlackBerry App World and install the Ugly Sweater expansion pack. If you already had Avatar Builder open, you'll want to exit out of it. When you re-open the app and create a new avatar, you should see the additional category on the right hand side along with the normal features and clothes. Choose from the many unstylish sweaters, then decorate it with a candy cane, a moose, a snowman or one of several other tacky items. Of course, you can still save, share, or set the avatar as your BBM profile picture from within the app.
If you don't have Avatar Builder installed already, you can grab the guy's or girl's version from the links below, as well as the Ugly Sweater Expansion Pack. Just remember, you must have both installed in order to see the new features.
Download Avatar Builder Girl's Edition
Download Avatar Builder Guy's Edition
Download Ugly Sweater Expansion Pack