Apple has begun rolling out tvOS 13.4 to all compatible Apple TV users as a free upgrade. However, unlike iOS 13.4, iPadOS 13.4, macOS 10.15.4, and watchOS 6.2, this update is boring. There’s only bug fixes and stability/security enhancements onboard. Granted, this isn’t a bad thing, but if you install it, don’t go looking for new features.
That being said, in order to install it, visit the Settings app in your Apple TV. You should see the update waiting to be installed.