The defending French champions are 16th in the Ligue 1 table after taking only four points from five games.
"I will make a call to our people," Girard told a news conference on the eve of their group B opener on Monday. "Tomorrow, it has to be hell for our English friends.
"I hope we will have 30,000 supporters, not 30,000 viewers. This is really important to me. We have been living hard times but we had so many good ones in the past three years."
Only five Montpellier players have played in the Champions League, a tally of 22 games, but the players believe they can still upset Arsenal despite being obvious underdogs.
"We are all very excited, happy to enter this competition," centre back Mapou Yanga-Mbiwa said. "It was one of our dreams, we were expecting that. Tomorrow, we will have to be right on time."
The 23-year-old, who won his first three caps with France in the past two months and was linked to AC Milan in the media during the transfer market window, will face a test against more experienced players.
"It is the time for us to measure up in the Champions League," he said. "We will have to be at our best."
Girard believes his players will be fully focused on Tuesday for the greatest game so far in the club's history.
"It is fabulous for the club, extraordinary for the players," he said. "We led this bunch of cheerful blokes to the highest level, a competition fought by the best 32 European clubs.
"I know that everybody is wondering how big their margin will be but we will be there."
