After Apple released the first official tvOS update, namely version 9.0.1, a new beta 2 of tvOS 9.1 of what will be the first major update of the operating system of your new Apple TV was released yesterday. tvOS 9.1 Beta 2 is now available for developers and can be installed on the Apple TV either via OTA or iTunes.
If you had already installed the previous version, the first fir TVOS 9.1, you can go to system settings and look for the upgrade, or wait to be downloaded automatically if you have active automatic updates. If this is not your case and you have no Beta installed then you can not use the OTA updates, and you have to use iTunes to install this second beta.
For this you need a USB-C cable to connect to your computer and open iTunes. You need to download the firmware file to your computer and manually upgrade to this new version. Once you have already installed itself and then can use the much faster and comfortable, OTA updates in future releases of Beta versions.
This second Beta, as the first, does not introduce major changes. Yesterday appeared in the first Beta able to use Siri to Apple Music, which Apple added manually to the level of their servers without upgrading anything. That function is maintained in this second Beta but for now we do not know any other variation worthy of highlighting.