Here's an explanation on
Simplicity
Here's what you can try:
Put the top on inside out. Where it bows away from you on the side pull together the extra fabric and pin, like is shows at the top of the simplicity page. You should end up with the point of the dart towards the center of your breast (but not all the way in the center, this causes bullet-boobs!). The line of the dart should end up somewhat like this:
Now put it on normally, and see if it lays nicer. Even if you're not a sewer, you can probably still sew it by hand.