You'll be presented with a 4-character code, which is what you'll use to connect the app with your Plex account. In your browser on your desktop or mobile device, go to plex.tv/link and ensure that you're signed into the appropriate Plex account. Make sure your TV has an internet connection. Open the Samsung Smart Hub or Samsung App Store, depending on your model, and sign in if necessary. Select recommended apps from the main screen and either browse or search for Plex. Select Install from within the Plex app screen and let the TV install the app.