I am unable to use Apple TV on my Smart TV

What is your model smart TV? Not all TVs can have the Apple TV app, but if the app is available on your TV, then you should be able to use that.

Unsupported TVs can connect an external streaming device that supports the Apple TV app. These external streaming devices include: Apple TV box, or Roku, Fire TV, Nvidia Shield, Xbox, PlayStation, ‘Chromecast with Google TV’ dongle, or select TV provider set-top boxes.

Get the Apple TV app or Apple TV+ app on your smart TV or streaming device - Apple Support

Watch on these smart TVs and third party streaming devices - Apple Support

How to watch Apple TV+ and more - Apple Support

Users will need to sign in to the Apple TV app on third party devices, through the in-app side bar, Settings﹥Accounts.

Alternatively, some TVs and external devices support AirPlay streaming from mobile. This feature can only be added to a model from its manufacturer. The Apple TV box supports AirPlay, so do some third party devices: List of AirPlay 2-enabled smart TVs and third party streaming devices - Apple

Just try to mirror the phone with smart tv it should be easy to go .

1. Check Compatibility: Ensure your Smart TV is compatible with Apple TV. Most Smart TVs are compatible if they have HDMI ports.
2. Connect Apple TV: Verify that your Apple TV is properly connected to your Smart TV using an HDMI cable. Make sure the cable is securely plugged into both the Apple TV and the TV's HDMI port.
3. Select the Correct Input: Use your TV remote to select the correct HDMI input where the Apple TV is connected. You may need to cycle through the inputs to find the right one.
4. Power Cycle: Restart both your Apple TV and Smart TV. Unplug them from the power source for about 10 seconds, then plug them back in and power them on.
5. Check Apple TV Settings: On your Apple TV, navigate to "Settings" > "Video and Audio" and make sure the correct resolution is selected for your TV.
6. Update Software: Ensure both your Apple TV and Smart TV have the latest software updates. Update if necessary.
7. Test with Another HDMI Cable or Port: Try using a different HDMI cable or port to rule out a faulty cable or port issue.
8. Reset Apple TV: As a last resort, you can reset your Apple TV by going to "Settings" > "System" > "Reset" and selecting "Reset and Update."

If these steps don’t resolve the issue, there might be a more specific problem with either your Apple TV or Smart TV, and contacting Apple Support or your TV manufacturer’s support may be necessary.