Using the tip of your blush brush, apply a sheer amount of your darker color just slightly above the cheek hollow, starting from the hairline and blending it down around your cheek. You want to create a shadow here.
To create a more defined jawline, go ahead and apply the darker color along the jawline. Work the color just under the face too. Make sure to blend well!
If you want to sculpt your nose to make it appear thinner or straighter, apply the dark tone on the side of your nose, very lightly and blend well.