Hi Eternity,
Schiphol is the only airport near Amsterdam. It is more expensive to fly there then for instance Rotterdam airport but the connexion to Den Helder is pretty good.
You can take the train from Schiphol to Amsterdam Sloterdijk and take a direct train to Den Helder from there. The train from Schiphol to Amsterdam Sloterdijk leaves every 15 minutes and from Amsterdam Sloterdijk to Den Helder leaves every 30 minutes.
Going to a diffirent airport is a possibility but will give you more trouble getting to Den Helder.
Hopefully is this helpfull to you.
Enjoy your stay in Holland