On the TV, you should take what DHCP hands out. You can go to your router and set the DNS there, and point it to whatever you need. If you want to manually enter DNS on the TV itself, you will have to use static IP addressing and make sure the router does not reallocate that IP address. Depending on your setup you might be able to do a DHCP reservation for that IP, or allocate outside of the DHCP range.

I believe the link provided by /u/j2225 is not for the right TV. Those menus don't look at all like what I see on my Sony or other Android TV devices.

https://www.sony.com/electronics/support/articles/00013283#:~:text=Select%20Settings.-,In%20the%20Settings%20menu%2C%20select%20Network.,Static%20and%20then%20press%20ENTER .

Why do you need to change them? Defaults work fine.