Forren arrived at St Mary's on a very strange day for the club, when Nigel Adkins was surprisingly fired and quickly replaced by Argentinian boss Mauricio Pochettino.
"I never spoke to Nigel," said the defender, who is expected to make his Premier League debut against Manchester United on Wednesday.
"I knew that there was a change and that the new manager wanted me here. For me it was never a problem, I was happy to be here and have an opportunity to play for Southampton.
"It has always been a dream to play in the Premier League. After a chat with Nicola (Cortese, Southampton chairman) there was no doubt for me with the plans he has for this club in the future.
"To be a part of that was hard to say no to, it is a team that is on its way up and a team who wants to play football - I was sure this was the right club for me. The club really wanted me and this feels the right club to play football in.
"All of my friends and family in Norway are happy for me to be in the Premier League, everyone loves the Premier League in Norway.
"Of course I have some friends who are United fans but if I do well and we get the three points I think they will be okay."
Forren also admitted that former United striker Ole Gunnar Solskjaer, who was his manager at Norwegian side Molde, played a big part in persuading him to further his career in England.
"For me he (Solskjaer) has meant everything to me, he is a great coach and I have taken big steps because of him," he added.
"I spoke a lot to him about the move and he really wanted to give me this opportunity so I have to thank him for that.
"I haven't spoken to him in the last week but maybe I will give him a call soon. He thinks it is a good step for me and a club on the way up."