Things You'll Need
Instructions
Place both Nintendo DS systems on a flat surface no more than a foot away from each other.
Turn on both Nintendo DS systems and start the Pokemon save file in each game. Travel to any Pokemon Center in both games.
Go up to the second floor of the Pokemon Center.
Press "A" in front of the lady at the center desk to begin the trade process.
Save the game when prompted to do so and go into the union club to begin trading. Do the same with the other DS.
Talk to the person in the Union Club and select "Trade." Repeat with the other DS.
Select "Darkrai" on the other DS. Select any Pokemon from your DS. Initiate the trade by selecting the "Confirm" option.