Diet is first and foremost. You have to structure a diet that in on point and maintainable for 45lbs of fat loss. My diet may not be right for you as your diet may not be good for me, everyones body is different.
Then cardio is a must. Start now with a few days a week plus your workouts and increase as you get closer to show date. Remember fat loss does not need a high HR, just moderate so dont go out kiling yourself.