He told MUTV: "I feel a wonderful amount of relief now to actually be here at Manchester United and I'm now getting myself prepared for the games that are coming up.
"It is a dream to wear the Manchester United shirt and it will also be a dream to win the title which we will all be working for this season.
"I feel like I have grown a lot, particularly with a year at West Ham. I think every different club in football you are with, be it in Italy, Spain or Brazil, you learn different things and you try to take things from each club.
"It is a huge learning curve but I feel I have grown as a player now I'm just getting ready to play for Manchester United.
"It's very important to be happy myself but also to be able to make the people who support Manchester United happy."