I think you do fit it to your bust. It's worth searching for other pattern reviews as it might give you an idea how much ease it will have. Or you could have a go at grading your pattern to suit your size.
Is it a multi size pattern? If so, would it be possible to take the size line at the bust and then draw a new line to meet the size line at the waist then so the same from the waist to the hips?
Otherwise I would fit the bust as you'll then be able to fit the shoulders and arm holes/sleeves as the proportions should be right. Then increase on the waist and decrease on the hips. As others have said its easier to change the waist and hips than the bust.