Pick up free tickets there for a shuttle boat to the memorial. The tour begins with a short film about the attack, then you board the boat to see the memorial itself. You may want to take a lei to place at the far end of the memorial, where names of the dead are carved. The island of Oahu is small enough that no major attraction is terribly far from Honolulu. If possible, you should plan to see some other parts of the island.
Several sights are very close to the city.
Guided tours are available. This area is also the windsurfing center of Oahu. Hanauma Bay is quite popular, and at midafternoon you may find yourself peering into the masks of other snorkelers rather than at fish, so go early. Finally, before departing Honolulu, check out the Pacific Aerospace Museum in the main concourse of Honolulu International Airport .