Post & interact with comments – Computer – YouTube Help

Open the YouTube app on your phone. Make sure you’re signed in to the same Google Account on both devices. A pop-up will open on your YouTube app, asking you to connect to YouTube on your TV. Tap Connect. Comments for the video you are watching on your TV will load on the YouTube app, allowing you to seamlessly post and interact with them.

https://support.google.com/youtube/answer/6000964?hl=en&co=GENIE.Platform%3DDesktop