McLean moved to Valley Parade last week after falling out of favour at Hull City, where he had been since joining from Peterborough United in 2011.
"It had been in the press that Aaron was linked with us and a few other clubs were also mentioned. Looking at some of those other clubs mentioned a lot of people would probably have said we had no chance of getting him," McArdle told reporters at a press conference.
"But the fact that he's here shows the club's ambition and from his record and from playing against him when he was at Peterborough, I know that he's a real handful. I didn't enjoy playing against him. He scores goals, he works hard and is everything that we need and if he can hit the ground running it will be a massive boost to the fans and everyone else at the club."
"He should suit Hans (James Hanson). Everybody knows what Hans is all about and if they can strike a good partnership up I'm sure Aaron will stick plenty of chances away."
McLean has recently been on loan at Ipswich Town and Birmingham City.