Mourinho has told the Frenchman to be patient in his desperation for a starting spot and praised the 21-year-old’s improving attitude.
Martial was touted for a move away from Old Trafford over the summer, two years after joining United from Monaco in a £59m deal.
But he has scored as a substitute in United’s first two games of the season and Mourinho said: “We’re using him well and he’s coming with the right attitude.
“We had a conversation about the future he has here, and I think he has a good connection on the pitch with Paul Pogba, with Romelu Lukaku,
“He’s growing in confidence, and of course, two periods of 20 minutes and he’s scored two goals, so for his confidence it’s good.
“He wants to play, of course he wants to start, of course he wants to be selected for the national team, of course he wants to go to the World Cup, so that’s good.
“I can’t play Premier League, Champions League, FA Cup and EFL Cup with 11 players, I need a squad.
“He’s working well, he’s working really well. His professional level has improved, he’s working much, much better, so we are happy.
“We have lots of hopes with him and obviously he has to be happy now, and he can only improve.”