Adjust the sliders to your advantage (max out the user sliders and decrease the computer AI sliders).
Once the sliders are adjusted, this should be easy. While you can throw this from the opponent's 30 yard line (the one closer to the end zone you need to score in), I recommend throwing the pass from your own 40 (the one on the opposite side of the 50 yard line from the end zone you're going to score in). If you do it from your own 40, you'll also unlock "Complete a 60 Yard Pass".