Set up for the smith machine shoulder press by setting a bench down in the smith machine and adjusting the back to a 90 degree angle.
Sit down on the bench and adjust the position so that the bar comfortably comes down just in front of your face.
Un-rack the weights and bend your elbows slightly. This is the starting position for the movement.
Slowly lower the weight down until the bar is just below chin height, pause, and then raise the bar back to the starting position without locking your elbows out at the top of the movement.