The former West Brom ace completed his move from The Baggies to The JJB on Tuesday in a £5.3million switch.
Koumas has two years experience of England's top-flight but has spent the last two campaigns in the Championship.
After Wigan's lofty bid was accepted, Koumas jumped at the chance to sign and is looking to repay Chris Hutchings' faith in him.
"I'm delighted it's all done now and I can look forward to playing in the Premiership," he told Sky Sports News.
"It's where I've wanted to be for a while so I can prove what I can do. It's all about playing in the Premiership.
"I'm at an age now where I need to be playing there. Wigan have given me the chance to come here and do well.
"Wigan is a great move for me. They've paid a lot of money for me, so I can't wait to get started and repay the faith the manager has shown.
"They are spending money. They are looking to have a right go next season. I'm looking forward to it. Once that bid was accepted I was delighted to sign."
Sky Sports