To make a humbucker wind two identical coils. Humbuckers use two bobbins, which are usually wound in the same direction, however the path to ground must go in opposite directions as shown below. If we labeled the start of each coil A and the end B.
Ground -> Coil 1 A -> B -> Coil 2 B -> A -> Hot
The poles on coil 1 need to be north and on 2 south (or visa versa).
The fifth wire, the shied wire, is soldered to the metal baseplate present on a humbucker. A pair of singles wouldn't have a baseplate so it'd be an idea to build one - it gives a base to hold everything togther too.