Pokemon Black

So I've finally got Pokemon black. So excited. But now I try to trade my legit Celebi over from my Pokemon diamond game to the black by the means of which I'm used to. Getting my friend codes, registering them and going to the trading area upstairs at the pokemon center. But I tried to register my Black friend code in my Diamond, and it said it was a "wrong code" and I tried to register my Diamond friend code in my Black, and it said the same thing.

How on earth am I supposed to get the Celebi, and how on earth can I register my friend codes to each game!?

Pokemon Black cannot Trade with any of the past DS Pokemon games. In order to get Celebi and the three legendary dogs onto your game you need to go to Castelia City. You have to talk to a guy in one of the buildings. He'll ask for a phrase, answer him with. Everyone Happy Simple Connection. This unlocks a feature on the main menu of the game. This will send out a DS download play. Now get another DS with Pokemon Pearl, Diamond, and Platinum Heart Gold and, Soul Silver. Don't go to the game Menu instead go to the DS menu and click on Download Play. You should be able to send your event Pokemon over to Pokemon Black then.

Because of the difference in area between regions, the Unova region and the Kanto, Johto, Hoenn and Sinnoh regions can not trade with each other. What you need to do is take two Nintendo DS's and then take the Celebi of yours and put it in the PC. Once you reach Castelia City, go towards Route 4. Just don't leave Castelia City. In a building at the very back alleyway of Castelia City, there is a building with a Clown and Researcher on floor 11. Talk to the researcher. He asks you for two passcodes. Enter in "Everyone Happy" then he asks for a second code. This time you enter "Simple Connection" and thus this unlocks a special way to send Celebi, Entei, Raikou, and Suicune from the events over. This will unlock Zorua and Zoroark in Black and White. Later on, you can use the Pokemon Transfer Lab to send other pokemon over from D/P/Pt/HG/SS

Oh alright thank you both so much

No problem glad to help out. ^_^

I finally got to the point where I can open the relocator, but when I try to send my Celebi over from my other pokemon game (Diamond) it gives me an error message stating that there was nothing to be sent over. Am I doing something wrong?

If its in your party you can't send it over. Other then that I have no idea what would be wrong.