Parking
You can park for free almost everywhere at the entrances to the dune hiking trails in the direction of Noordwijkerhout. However, you will have to walk a bit if you don't want to be off the beaten track on the beach. Depending on where you park, it's a 20 to 30-minute walk to Strandopgang 21 with the beach bars of Noordwijk.
Alternatively, you can buy a day ticket for €10 from one of the parking ticket machines at Strandopgang 21.