Instructions
Find someone who attended the Celebi Event at Gamestop stores from February 27, 2011 to March 7, 2011.
Offer a valuable Pokemon in exchange for the Celebi to encourage the trade. Shiny Pokemon, Legendary Pokemon and Pokemon from Nintendo Events may have equal trade value for a Celebi. You may have to offer multiple valuable Pokemon to complete the deal.
Set up your Wi-Fi Connection, then go to any Pokemon Center in the game and descend the stairs to the right. Talk to the first lady behind the desk and she will give you a Pal Pad. Speak to the woman standing behind the middle counter and she will give you a friend code.
Ask the person you're trading with to set up their Wi-Fi Connection, get a Pal Pad and a friend code. Pick a date and time for the two of you to trade. You don't have to pick a place to trade, since you will be trading by Wi-Fi. Exchange friend codes with each other.
Put the Pokemon you agreed to trade for the Celebi in your party. Go downstairs at any Pokemon Center when it's time to trade. Speak to the lady who gave you your friend code. She will take you to the Wi-Fi club where you can trade with the person who owns a Celebi.