When you paint realistically you don't want the painting to look too flat. One way to create deapth is to add shadows. Do you see the shadow under the hand/wrist in the second picture? Then compare it to the picture above.
You have to make sure that the painting is dry before you apply the shadow. To make the shadow transparent you can mix the oil color with a fair amount of medium. Then you will be able to see some of the background through the shadow.
This is just WIP (work in progress), I'll give you a full step-by-step tutorial when it is done.