The Algerian posed for photographs before taking a seat and answering questions about his move to the Etihad Stadium.
"The most important thing is I'm here, happy and starting a new challenge and a new life", he said."[January] is in the past, I'm here now.it's what happened before and I'm happy now. "This does not affect me", said Mahrez, who only cost Leicester £400,000 when they signed him in 2014.
"I think he will do very well and the thought of Leroy Sane on wing and Riyad Mahrez on the other is very exciting - he will give Pep Guardiola more options in attack and it will be interesting to see the various attacking combinations City can use".
Mahrez, 27, arrives at the club following a failed move in January.
"We haven't talked about (Pep's expectations for next season) yet. If I'd moved sooner maybe I wouldn't have been happy, I don't know".
He said: "He's a big manager, he's won a lot of things, made history with this club".
Asked if he was anxious about the challenge of getting into the City side, Mahrez said: "No, I never thought about that".
Maguire has shown the requisite mental strength to play in the big games for his country and that would be easily transferred into the top of the table and Champions League clashes. It's a Champions League team, who want to win trophies every season.
Maguire starred for England at the World Cup, scoring against Sweden as the Three Lions reached the semi-finals for the first time since 1990.
Four years ago James Rodriguez had already made a name for himself at Porto and Monaco coming into the World Cup in Brazil but at the tournament he made himself into a superstar.
"He's a very good player", Mahrez told reporters, about his former team-mate. They deserve a lot of credit for what they have achieved because reaching the semi final is very, very hard.
"They have everything to try to win the Champions League".
Manchester United are reportedly preparing to launch a sizable bid for England defender Harry Maguire.