How do you change a screw in pot light bulb Cannot unscrew the existing bulb?

If you cannot unscrew the existing bulb, first ensure the power is turned off at the circuit breaker for safety. Use a rubber grip or cloth to increase friction and try turning the bulb again. If it’s still stuck, carefully apply penetrating oil around the base and let it sit for a few minutes, then try again. If all else fails, you may need to remove the fixture to access the bulb from behind.