The Frenchman had been continuously linked with a return to Old Trafford in recent weeks and finalised his move on Monday afternoon where he successfully completed a medical at Carrington.
Man United announced his arrival to fans in the early hours of Tuesday morning and he has since been meeting with his former team-mates.
Speaking about Pogba, Mourinho insists it will now be a process of trying to get the best out of him.
“We need to get the best out of him and this will be a process,” Mourinho said.
“So if he needs protection, I am here to protect. I know some people think that he arrives here now and, the first time he touches the ball, he scores, but I’m here to protect him and give him the best conditions to be what we think he is going to be, which is a football player for Man United, a reference for this club. I’m so happy.
“He’s a very young player, an unbelievable midfield player with such physicality but, at the same time, such agility, co-ordination, skill. He has everything.
“What he has to learn now is how to play with us because I always say that in football you can be a super player, like he is, but a team is a team and you need to learn how to play in the team, and the team needs to learn how to play with you.”
“I can feel that when I speak with him for the first time. I’m feeling now when I see him at the training ground with people he knows since he was a kid. He doesn’t look like a star,” he added.
“He looks like a kid who is back to his old school and is finding people that he cares about and people that love him a lot. So I believe that, after a couple of days, he will feel like he never left the club.
Pogba left Old Trafford four years ago after becoming frustrated with Sir Alex Ferguson over a lack of playing time but will return at the heart of Mourinho’s new side.
He’s one of the best in the world and has the Ballon d’Or on his list of ambitions on his list at Old Trafford so it’s no surprise to hear Mourinho trying to provide him with the right environment.