The Frenchman was on the verge of a £9million move to Birmingham after the Latics agreed a fee but the deal collapsed when the 24-year-old altered his demands.
N'Zogbia was left out of the side which beat Tottenham at White Hart Lane on Saturday and even reportedly tried to resurrect a deal with Blues on transfer deadline day.
Martinez admits the player has plenty of work to do to get back into favour at the DW Stadium.
Enlarge Enlarge Pull your socks up: After his move to Birmingham fell through boss Roberto Martinez has N'Zogbia to fight for his place at Latics
'He is an important player for Wigan. Now it is a matter of him showing the players how focused and dedicated he is to help the team achieve things,' said the Wigan boss.
'Charles has been through a turbulent period but he wanted to stay at Wigan so his frame of mind is the right one.
'Now he has to show how ready he is on the training ground to see if he can be prepared to help the team get a result.
'You need to prove yourself, show how much you care about the team and the club before yourself and if you do that your talent will speak.
'When you have talented players like Charles N'Zogbia you want them in the football club and now it is down to him to show how much he wants to play for us.'
Martinez alluded to the effect the actions of N'Zogbia - he handed in a transfer request on the eve of the season - have had within the squad.
'What you get with that sort of result (at Tottenham) is that we have real competition for places and that is quite clear," added the Spaniard.
'There is a real team spirit in the dressing room. We have eight new players and lost 10 so you can understand the dressing room loses certain rules and certain responsibilities and it is very easy to have individuals playing as a team.
'To have that feeling as a group of players fighting for each other and understanding what the next move is in relation to my team-mate that is how you become a team.'
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