United had little trouble dispatching Club Brugge in the play-offs, but their first Group B game ended in a disappointing 2-1 defeat to PSV Eindhoven.
Van Gaal believes it will be tough for United to make the last 16 if they do not win all their home games, so he wants a victory from his players in their Old Trafford meeting with the Bundesliga side.
''I think in the Champions League you need to win all your home matches otherwise it shall be very difficult,'' said Van Gaal, who lifted the trophy with Ajax 20 years ago.
"It is important we shall win."
United may be top of the league and big favourites to win on Wednesday, but Van Gaal is yet to bring the enterprising football the club's fans desire.
He insists the club are heading in the right direction under his stewardship, however, and there is no doubt in his mind he can win the league and Champions League during his time in charge.
''That is realistic because I did it everywhere,'' said the 64-year-old when asked if he could win silverware with United.
''Reaching the (Champions League) final is also an aim and winning the final is a little bit of luck.''
Bastian Schweinsteiger, who won the Champions League with Bayern Munich, shares his manager's optimism.
''Yes
I think (we can)," the German midfielder said when asked if United could go all the way to Milan and lift the trophy.
"But of course first of all we have to do our work.
''As the manager said we have to win our games at home.''
One man who could prove to be key to the outcome of Wednesday's game is Nicklas Bendtner.
The former Arsenal striker never lived up to expectations during his time at the London club and also hit the headlines for the wrong reasons off the pitch.
His troubles continued at Wolfsburg, where he was made to train on his own after falling out with Hecking last year.
But the 27-year-old scored a vital equaliser and the winning penalty in the club's DFL-Supercup victory over Bayern Munich in August and is now a key squad member according to his manager.
"He has reacted very well
I have seen that in training," Dieter Hecking said.
"He did have problems before but in his time at Wolfsburg he has come on a lot.
"Certainly in the last four to six weeks I have seen more development from him
He is on the right track
That is clear.
"He shows that in training, perhaps with less of the extravagance that he showed in England before, so I think he is on the right track and he will definitely be keen to play."
Source : PA
Source: PA