Adjust to the shoulder press position, then the seat height to allow the handles to be just above your shoulders when seated. Grip the handles at slightly wider than shoulder width, with your palms facing forward and knuckles pointing upwards.
Start the press by driving your hands upwards, like your moving your biceps towards your ears. Press up to a point just before your arms are fully extended, then lower back down where your elbows are bent a little past a 90 degree angle, don't go too low where the weights begin to clash. Keep your wrists aligned with your forearms at all times and have a straight back against the seat to avoid your elbows tucking too far back. Repeat for the desired amount of repetitions then rest the weight gently at the start position. (Whole paragraph read straight)
Perform the exercise in a controlled manner at all times and Ensure that your back stays straight and remains against the pad.
Fitness for all, for life.