Pull the wire off the spark plug on top of the Ariens engine.
Unscrew the old plug with the spark plug socket wrench, turning the wrench to the left to remove the plug.
Set the gap on the new spark plug to the measurement recommended for your particular engine, using the gapping tool to bend the L-shaped wire on one end of the plug. A common plug gap is 0.03 inches for many small Briggs & Stratton engines, but models vary on Ariens snow blowers so check your engine for specifics.
Insert the threaded end of the new plug into the socket on top of the engine and tighten with the wrench,
Connect the engine wire to the tip of the new plug.