TvOS 14 beta supports Apple TV 4K and Apple TV (4th generation) only.
If you tap Install Tonight, connect your device to a power cord at night and your device will update automatically by morning. Or tap Later and choose Install Tonight or Remind Me Later. Tap Settings > General > Software Update.Connect your device to a power cord and connect to Wi-Fi.Tap the configuration profile in Mail and follow the installation instructions. On your Mac or PC: Save the file to your hard disk and email it to an account on your iPhone. On your iOS device: Download the configuration profile directly onto your iOS device and follow the installation instructions. Download the configuration profile from the download page.IOS Beta Software Installation Using the Configuration Profile