Select a single closest matching shade or mix two shades to match the complexion of the skin.
With the help of a brush apply it over the dark spots, blemishes, and dark areas and blend it smoothly with the help of a brush or beauty blender.
Layer it with a foundation base.
Then apply it above the foundation base on areas such as the under eye, the center of the forehead and nose bridge, the chin, etc to highlight the areas.