How long has it been since you delivered? You should be able to start light exercising right after the anesthesia wears off although I know I would be paranoid about the incision splitting open too.
You'll want to:
-Progress at your own rate. Gentle exercises are important in order to facilitate healing of the muscles.
-For the first two or three days, support your incision with your hands or a pillow for comfort.
-Relax and breathe deeply throughout and between the exercises, exhaling on the effort. Do NOT hold your breath.
-Support your head and shoulders with a pillow for comfort.
-Start by doing each exercise twice.