Although instinct will lead you to step on the brake, don't do it. Don't step on the clutch either, because by doing so you are eliminating the engine brake, which is very helpful in these circumstances.
What you have to do if your car skids in the back is to lift your foot off the gas pedal. Also, the use of the steering wheel is key in this situation. You must turn the steering wheel towards the same side, towards which the rear wheels are going. Also, you have to try to stay calm and make a smooth turn of the steering wheel, without brusqueness, that is, keep control of the car.
