You can type Siri queries using the onscreen keyboard on Apple TV, a connected wireless Bluetooth keyboard, or an iPhone or iPad. When Type to Siri is turned on, you can also dictate text instead of entering it.
Siri understands a wide range of queries, and intuitively applies them to the current context whenever possible.
Go to Settings 
on Apple TV.
Go to Accessibility, then select Type to Siri to turn it on.
Press 
on your remote, then do any of the following:
Enter text using the onscreen keyboard: Navigate to an onscreen character, then select it.
To switch keyboards, press 
, or select letters, numbers, or special symbols onscreen.
Enter text using a wireless Bluetooth keyboard: Make sure the keyboard is connected to Apple TV, then use it to enter text. See Connect Bluetooth devices to Apple TV.
Enter text using an iPhone or iPad: Make sure the device is set up to enter text on Apple TV, then use it to enter text. See Use your iPhone or iPad as a keyboard on Apple TV.
Dictate instead of type: Press and hold on the remote, say the text you want to enter, then release the Siri button.
Select Done.