Turn the key to the "Off" position in the ignition and remove. Unscrew the two screws with your nut driver which hold the control panel to the snowblower.
Grasp the spark plug boot with a tongs and pull straight to remove it. Place your socket wrench over the spark plug and turn it counterclockwise to unscrew it.
Remove the spark plug and screw in the new one clockwise until hand-tight.
Place the socket wrench back over the spark plug and continue to turn clockwise until snug. Snug is what you are aiming for here -- ratchet it too tight and you could strip it out.
Push the rubber boot back over the spark plug until it clicks into place. Screw the control panel back on to the snowblower.