First, you must have beaten the pokemon league. Then you go to the town, city, etc. The farthest west that is by where you started. You go to the sailor's house (by the dock across the bridge) and talk to the kid. He will say something about Darkrai in his sleep. Talk to the mom, then talk to the sailor, and go to half moon island or something. You go further into the island and enter the place. You will see Cresselia, and he will go away. The Lunar Wing will be where he was. He will be like Mesprit, fleeing and will be hard to catch. Then bring the Lunar Wing to the kid and he will wake up.
