Follow the long black hose on the side of the snow thrower's motor. As it gets closer to the engine, a small piece of metal will be protruding from the hose. This is the spark plug.
Pull the hose off the spark plug. It might take a little strength to do it, but it can be done.
Pop the spark plug out of the other side of the hose. Remember the way the plug was connected in the hose so that you put the new one in the correct way.
Place the new plug in the correct way into the hose connector.
Place the other section of the hose onto the plug.