thar was an event that's where you get it
Use the Poke Relocator to get the most recent Event Celebi onto White (no other Celebi works). Go to the girl in Castelia City who you talked to to register Zorua in your pokedex. Make sure there's a space in your team and you have Celebi in hand, along with at least one pokeball of any kind. If your Celebi and Zorua get on happily, Zorua is yours.
You need a 'Fateful Encounter' Celebi.
No,it has to be the Celebi that was being given away at the Pokemon Black and White Mall Tour or the one that was given away at GameStop.
No, but you can use the Celebi that can be obtained from Gamestop to activate the Celebi event to catch Zorua and evolve it into Zoroark
Step 1 - Get two DS consoles, one with Pokemon White, one a SoulSilver/HeartGold with the 13th movie Celebi, most likely a Gamestop one. Other Celebi won't work, it must be a 13th movie one. Step 2 - Either use the Relocator, or if you have finished the game, the PokeTransfer Lab, to migrate the 13th movie Celebi over to Pokemon White. Full instructions on how to migrate, is in the manual. Step 3 - Save the game and put Celebi in your party. Step 4 - Go to Castelia City, and go up the first 'street', the easternmost one. Step 5 - One building has a woman reading to a quiet boy. The boy is Zorua, speak to it, and Celebi will appear. You'll then be allowed to take Zorua, choosing a ball to put it in (no battle occurs).
You can not collect a celebi on black or white. You need to transfer from the 4th generation.
Zorua can't be captured in any 4th generation game (Diamond, Pearl, Platinum, HearGold, SoulSilver), as it is a 5th generation Pokemon. To get Zorua in a 5th generation game, you have to have gotten Celebi from the Gamestop Event on one of the 4th generation game. Then use the Relocator in Castelia City (Password: Everyone Happy Simple Connection) While Celebi is in your party in Castelia City, Zorua is the boy on the first floor of the GameFreak building in Castelia City. Talk to the boy, and he turns into Zorua. Battle it, catch it, and you have a (legit) Zorua.
Yes you need Celebi but you can trade on GTS
Yes, in Black 2, you can get get Zorua however you won't be given it until you make it to Driftveil City. One of the former 7 Sages will give you Zorua, it's part of the storyline so it cannot be missed however you need to have 5 or less Pokémon in your party in order to be able to accept Zorua.
Nope, you can only use it once. If you try to use Celebi twice for the event, nothing will happen. You will just stand there, just like if you didn't have Celebi.
Everyone Happy Simple Connection. The machine is the Relocator, which is used to transfer the Shiny Beasts of Johto and the Event Celebi to Black/White. If you don't use the Relocator for these Pokemon, it won't activate the events to get Zorua and Zoroark.
One way to find Zorua is to have the Event Celebi from GameStop. If you have it. If you do, use the Relocator in Castelia City. (Password: Everyone Happy Simple Connection). Zorua is the boy on the 1st floor of the GameFreak. Have Celebi in your party when you talk to him then you can battle and capture Zorua. Another way is if you have any of the three Shiny Legendary Beast of Johto (again, from an event) and have captured Zoroark, you can breed Zoroark (PokéShift a Ditto if it's male) and have a Zorua Egg.