Pandora on Wednesday launched an application for the new Apple TV. You can find it by navigating to the App Store in tvOS, and scrolling through the Featured page where Apple currently has the app highlighted in the 'Best New Apps' category.
The new tvOS client is obviously somewhat limited compared to its iOS counterpart, but it will allow you to sign into your Pandora account and listen to your customized Radio stations. You can also access tabs like Create Station and Now Playing.