Pull the turntable up and out of the LG Microwave. This gives you access to the device that spins the turntable at the bottom of the microwave.
Remove any food or other debris stuck on the bottom of the LG microwave. This may be pushing up on the turntable, preventing it from spinning.
Fit the small turntable ring (this is a flexible device found directly under the turntable when you remove it) around the device that spins on the bottom of the microwave. If the ring has been bumped out of position the turntable is not going to spin.
Place the glass turntable back into the microwave. Make sure the grooves on the bottom fit into place over the spinning device. This ensures the turntable catches and spins when the cooking is activated.