Up until now, if you wanted to listen to Pandora on your Xbox One, you had to access it through Internet Explorer and use the web version. That changed today, as Microsoft has just released an Xbox One app for Pandora, available now in the Xbox One App Store. According to the app's description:
Great music discovery is effortless and free with Pandora. Just start with the name of one of your favorite artists, songs, or genres or composers and we will do the rest. It's easy to create personalized stations that play only the music you'll love
If you have a Pandora account, you can just sign in, or create a new account from within the app. You'll find the app (it's featured as of this writing) in the Xbox One App Store.