Forren joined from Molde earlier this month after rejecting the chance to have a trial at Liverpool.
"I never spoke to Nigel," said Forren. "I knew that there was a change and the new manager wanted me here.
"For me it was never a problem, I was happy to be here and have the opportunity to play for Southampton.
"It has always been a dream to play in the Premier League. After a chat with Nicola (Cortese, the chairman) there was no doubt for me, with the plans he has for this club in the future."
Forren could make his debut for his Southampton when they take on Manchester United on Wednesday.