Two new channels have been added to the Apple TV's lineup, PBS and Yahoo! Screen. Screen gives you access to episodes, clips, and digital exclusives from outlets like SNL, Comedy Central, ABC News, and more. You can browse either by category or channel in Screen, or use the search function to find what you're looking for.
PBS requires you to connect your Apple TV with your PBS account, Facebook, or Google+ in order to get the most out of the channel. You can view PBS featured content, or view individual programs, with many available based on your location. You can also view the full list of available programs alphabetically.
These channels should automatically appear on your Apple TV without the need for another software update.