Shoulder press with a bar is a relatively simple exercise that is done with one hand.
The trump card of this exercise is that it reduces the chance of injury to the area. Using a bar pushes you to balance the load, thus combining more muscles in the area.
Watch how to do Javelin Press in the video below
Alternatively, it can be done with a dumbbell (this is how I do it, to avoid using a bar because of lack of space).