The Bantams won the first-leg 3-1.
McArdle told talkSPORT: "They're still probably favourites in footballing terms but all the pressure will be on them, we can go down and enjoy the day.
"We know we can create chances and if we can nick a goal down there it makes their task even bigger.
"If you go down with a defensive set-up, you invite pressure. We know they'll have spells where they get the ball so it's important we get up the field and get the ball in the box."