The Spanish striker has moved to Stamford Bridge from Barcelona following the completion of a £5 million move this week.
Guiu is the Blues’ third signing of the summer so far, after landing Tosin Adarabioyo on a free transfer and Omari Kellyman from Aston Villa.
The 18-year-old says it has been a “dream” of his to play in the Premier League and believes he can “win a lot of trophies” at his new club.
“It’s an immense joy to sign for Chelsea and I struggled to sleep ahead of the journey here because I was so excited,” he said in a club interview.
“Ever since I was small, it was my dream to play in the Premier League. Now I have the opportunity to come here to Chelsea and I will work my hardest to be successful for the club.
“I think what’s most important [to start with] is that I adapt to my surroundings, which I’m sure will be easy, and then of course I want to win the Champions League and the Premier League for Chelsea.
“On a personal level, I want to help the team as much as I can by scoring lots of goals and I want to become the best centre forward in the world.”
Guiu also explained the reasoning behind his decision to leave his boyhood club and move to south west London.
“My main reason for wanting to sign for Chelsea was the football and sporting project the club is offering me here, and the trust everyone who works at the club is putting in me,” he said.
“The club has a very interesting plan with a lot of young and exciting players and I think we can do great things.”
He added: “I think it’s a very talented squad, full of top players who are very young, have a lot of quality and have a lot to offer.”
On manager Enzo Maresca, Guiu said: “I think he is a top manager and he did a fantastic job at Leicester, getting the team promoted to the Premier League.
“I think we will play great football under him and we can win a lot of trophies.”
