Ask an assistant to hold the shower door in place.
Loosen the screws on the hinges using a Phillips screwdriver. Do not remove the screws.
Slide the door slowly in the direction to which it needs to be adjusted.
Step back from the door while your assistant is still holding the door, and view it to determine whether it is even.
Continue to slide the door up, down or to the side until it is properly adjusted.
Tighten the screws on the hinges until the door is secure. Do not over-tighten the screws, because that could shatter the glass.