The Wembley clash will be the first since former manager Liam Rosenior was sacked and replaced by McFarlane.
"We want to attack the game," explained McFarlane. "We want to be aggressive in every phase of the game and we want to have complete control of it, and ultimately win the game.
"I think that's the best way to win games of football. I think that's the best way for this team to win games of football.
"But there's also an opponent who wants to do the same, so we have to be better than them in every area. That will be the challenge on Sunday."
McFarlane added: "Everything has been done that we possibly can. We’re working really hard to make sure the lads are as best prepared as they can be for what Leeds are going to throw at us and we know what we have to stand up to.
"They're a really good side that can cause you a lot of problems and we know the challenge we face, but the players are motivated to get to an FA Cup final. Everyone's on board and we're ready."