Things You'll Need
Instructions
Go to the Pokemon Center in any town. All the major cities have Pokemon Centers, so there should be one close by. It does not matter which Pokemon Center you go to, as they all have trading stations. Ask the person you're trading with to do the same with his Nintendo DS. Although the two Nintendo DS systems do not need to be right next to each other, the connection may fail if you travel more than 65 feet away from the other system.
Speak with the attendant at the Pokemon Center, and select the "Trade" option. Do not select the "GTS" option.
Select "Yes" when prompted, if you wish to save your game. Enter the room.
Select any Pokemon to trade on your DS, and then have your partner select "Celebi" on the other DS. Initiate the trade by selecting "Confirm" on both games. After the trade is over, you will have Celebi.