You can do this very easily without any hassle. First of all, you will have to make sure that your smart TV has a functional internet connection. Whatever smart TV you are using and it will have a smart hub or its equivalent where you can make changes to your profile and check out the settings. There you must sign in and then add plex to your apps from either the list of recommended ones or you could just look for it. You will now have to install it on your smart TV and you are now done!