Use the wall as support while you get used to being upside down (which can be scary), and gradually build up strength in the upper body. Learning to trust your upper body strength will happen gradually, so have fun with these poses and appreciate the wall as a friend!
Getting Into the Pose
From downward-facing dog with your heels pressed against a sturdy wall (figure a), activate your core and begin to walk slowly up the wall until your feet reach hip level. Press the feet firmly into the wall, and activate pada bandha. The hands should be stacked directly under the shoulders with the fingers spread wide (starfish hands; figure b). If you find your hands in front of the shoulders, walk the feet down and reposition them closer to the wall.
Holding the Pose
Press your fingers firmly into the mat, and press the feet into the wall for a fully active core. Draw the energy from the arms and the legs to the center of the body (figure c). For more sensation lift one leg off the wall, and reach the heel toward the sky. Switch sides. Concentrate on a slow, steady breath. Follow with child's pose.
Modifications
If you need to minimize pressure on the wrists, then try forearm balance instead. If your feet slide down the wall, then concentrate more on core activation by drawing the muscles of the pelvic floor up toward the heart.