How do I install the beta for tv ios
How do I install the beta for apple tv
Download the Apple Configurator 2.3 beta and the tvOS 10 beta Configuration Profile
Connect the ATV4 with a USB-C cable and copy the Config profile to the ATV4
Once it is there, go and check for software updates and it will pull down the beta.
In the past, one process was to first download the beta to your mac, then connect your ATV4, find it in iTunes, hold the option key and select 'restore' - follow the resulting dialog to locate the ipsw file, choose it and go.
Note:
You must have the latest beta version of Xcode 8 installed on your Mac before using a Restore Image to install iOS or tvOS beta software on a device.
See this document (linked from the download page...scroll down) for both processes:
I prefer a clean slate when working with a beta, so whichever process suits your workflow.