Sit against the wall with your elbows bent at 90 degrees in a shoulder press position.  Try to have as little space between yourself and the wall as possible.  So their shouldn’t be any gaps of space between the wall and your low back, and your elbows, wrists and shoulders should all be pressed as flat as you can against the wall.

Slowly press your hands overhead,making sure that nothing comes out of contact with the wall.  Press completely overhead, then retract the hands back down into starting position.  Do 3 reps

If you can’t maintain contact with the wall, get as close as you can, always working to get closer.