Determine which way you want the door to open. If you want it to open to the left, mount the hinges on the left. If you want it to open to the right, mount the hinges on the right.
Take a measurement 5-1/8 inches down from the door frame's header. Make a mark on the door frame at this location. Make sure the mark is on the door frame's exterior edge. This mark indicates where to position the top hinge's top edge.
Measure 10-1/4 inches up from the floor along the door frame and make a mark. This mark indicates the bottom hinge's bottom edge.
Calculate the distance between the two marks you already made. Divide this measurement in half. Mark this location between the two marks on the door frame. This mark indicates the center of the middle hinge.