You don't charge the glow plug, the glow plug goes in the top of the engine... You do charge the glow plug igniter though... Plug the charger in the wall, plug the charger to the igniter, once it is charged put the igniter ontop of the glow plug, push down and pull the cord, or if you have a starter box, put the flywheels on the starter box wheel and when you push down it will spin it.