It depends on the type of mount. If it is a fixed mount, then there will be 4 screws to remove. They are difficult to reach and it is a two person job. Check out my previous posts on this issue.
If you see four wood buttons, pull those, there are screws behind them. That removes the trim which should expose a black metal bracket with additional fasteners. Takes those out, but be careful the TV is attached to that bracket.
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