To activate YouTube on a smart Samsung TV using a computer, first ensure that your TV is connected to the internet. Then, open the YouTube app on your TV and select "Sign in." A code should appear on the screen. Take note of this code and go to the activation page on your computer (youtube.com/activate).
Sign in to your Google account if prompted, and enter the code displayed on your TV. Once done, click "Allow access" to complete the activation process. You should now be able to use YouTube on your Samsung TV with all its features available. This process may vary depending on model and software version so refer to Samsung's support page or manual for more detailed instructions.