Hi pcsos,
To turn on Ambient mode, press the Home button on your remote. Then, navigate to and select Ambient Mode. It should be to the left on your Menu screen and looks like a symbol with the leaves of a flower on it.
If you need more help, please reach out to Samsung Support at 1-800-SAMSUNG (ask for TVs), available 8 AM – 12 AM EST, seven days a week.
~Samsung Advisor