The defender arrived at St Mary's earlier this month, but was not involved for the draw with Everton seven days ago.
Having spent much of the past week bonding with his new teammates during a training camp in Barcelona, Forren says he is now ready to step up his involvement ahead of the trip to Old Trafford.
But, although he admits it would be 'perfect' to make his debut against the side he followed as a boy, the Norwegian does not expect to just walk into Mauricio Pochettino's team.
"To play on Wednesday would be the biggest dream ever," Forren told the press this afternoon.
"I'll fight for that and train hard, then we'll see if I'm in the squad. To make my debut at Old Trafford would be perfect, but I'm patient because I know it's hard to just come here.
"You have to show that you're good enough, so I'll train hard and get my chance when I'm ready."
Having spent his entire career to date playing in his home country, Forren admits it is a big step up to play in the Barclays Premier League.
But the 24-year-old says he is confident that the football experiences he has under his belt will help him make his name in England.
"The Norwegian league isn't as good as this one, but it's a high level," he insisted.
"Playing in the Europa League, Champions League qualifying matches and for the national team has helped me believe that I am good enough for this and being able to take the next step.
"I feel ready to play in the best league in the world, and I'm very happy to be here.
"For me, it's always been a dream to play in the Premier League," he continued.
"There has been interest in me for a long time, so I had to be patient and wait for the right offer and the right club.
"Southampton felt like the right club for me, and the plans fit me well in terms of the way the Club wants to play football. It's a team that is on its way up and a team that wants to play football.
"After my chat with Nicola [Cortese, Executive Chairman] there was no doubt for me about the plans he has for this Club in the future. The opportunity to be a part of that is hard to say no to."