If you turn up at one of the events you need to go into mystery gift and then accept from wifi. Once you have done this you need to go to a pokemart and speak to the guy in green, if you have a space free in your party he will give you the pokemon but you must remember to save your game right after you get it or you wont have it when you turn back on. If your having issues there should be a lady in there at the pokemon stand at the store, they are running a competition so it may be worth speaking to her anyway.