Google has begun pushing a Voice Remote feature to YouTube TV that will let users speak to the app to complete a number of various actions all without having to touch the display much. The one thing to take note of is that this isn't a feature which everyone will get a hold of at the moment as it seems Google is only pushing the feature to select users. The feature is likely already embedded within the app and Google seems to be enabling it server side with a smaller group of people for now, which means that it may end up rolling it out to more people in the coming days and weeks ahead.
Naturally, since this is a voice remote you can enable the toggle if the feature is showing up for you in the application and all you have to do is talk to the app after opening it up. There is also a floating action button, which you presumably need to tap first before the voice actions can be accepted. The voice actions should work for a number of things from changing channels to selecting a specific program to watch, or perhaps search for if you aren't really sure what you want to watch in the first place.
As this is seemingly a server side feature that Google itself is turning on there is no update needed to receive it, though you do probably have to be on the latest version of YouTube TV if you want it to be turned on server side, so that's something to keep in mind. Also worth remembering is that though the feature brings voice control, you will still probably have to tap the FAB button for things to work. That said if you have a phone with Google Assistant on it, you can have Google Assistant open YouTube TV and then all you'll have to do is tap the FAB button, then let the Voice Remote feature take things from their, meaning you should be able to get away with only having to touch one button the entire time.