With an adjustable sight... pick the style sight picture you want to use and adjust the sights to hit when holding that sight picture.
I prefer center hold. (the one in the center)
6 o'clock hold is popular for some, depending on their shooting technique. (first picture)
Never known anyone to use the last style though.
Use a gun rest, or rest your forearms and hands on the shooting bench when aiming to help steady your aim when working on adjusting your sights.