He has trained for the club and Spanish football is all pretty similar.
In Brazil, they mould their youngsters from a tender age and make sure they grow up playing 'the right way' so that they are fully adapted and ready for the style of the Brazilian leagues. That's just an example, though.
What I'm trying to say is that he has played for Spain (who play similar to Barca), has made friends with Barcelona players when playing for the youth team/playing for Spain, can speak Spanish and has played for Barcelona youth/"B"(?). He won't have much trouble settling in to the Barca team and I believe if he does well (which I think he will) he will replace Xavi one day.