At this stage its just a matter of repeating the process on other parts of her body. Select an area, slowly build up the dark shades.
The technical aspect of adding light and shade to parts of the body is the same in all aspects of this process. What makes it effective is the understanding the human body’s shape and how it reacts to light. Like how an arm is basically a cylinder, so it stands to reason you should color the arm like a cylinder (see c13).
The torso is probably the most difficult part to color, specially if its a woman’s torso. You have to deal with different kinds of contours and shapes. There’s the chest area, the collar bone, the breasts, the area where the armpits meet the side of the breasts, the abdomen, etc. (see c14)
To create the almost sharp shadows under her arms, select the shape of it using the Freehand Lasso Tool (L), feather it to 1-2 px, then use the Gradient Tool (G) to build the dark areas using one or two of the darker shades in Darken mode. Always play with the Opacity and direction to get the shade just right (see c15).
If there’s an area you can’t figure out how to color, don’t be afraid to look through different references. The more information you gather, the better your skills will improve.