how to watch tv on smart tv when have directv at home in different state?

You can't watch DTV sat on a TV in another state unless it has its own dish and receiver.

You cannot watch DirecTV itself as it is tied to your physical service address. This is important for local channels, sports team viewing, and taxes paid.

However, some channels will allow limited streaming even away from home. You would need to download the specific channel's own TV app and login with DirecTV's verification. This is assuming your "smart" TV is connected to the internet.

As a note, some channel apps might not work well on a "smart" TV (if at all). The alternative is a streaming device (Roku, Firestick, etc.) that you plug into whatever TV you have (even if it is not a "smart" TV).