If Android Smart-TV has the Google Play Store -app feature:
Open Google Play Store-app on the Android-TV
Search Singa, install and open the app
Choose Create an account or Log in - after that you will get an activation code
Go to the activation page with a mobile device or computer (https://singa.com/device), log in and enter the activation code
If the Android-TV doesn't have the Play Store -app feature you can use the smart-TV as external display by connecting the TV with a mobile device or a computer.
You are required to have a cable and possibly an adapter to connect phone or tablet to the Smart TV. Please note that your electronics vendor has the best information and suggestions about the cables and adapters compatible especially to your devices.
Directions to how to share screen from you computer you can find here.