Do a 'dry try' to assemble the whole thing but without the spring. That will make it much much easier. Then, pull the black out and hold it there with your thumb and your fist (to imitate the spring) and turn the spool with a long nose pliers, and you will see exactly how the whole thing works and a lot of questions will be answered. If not for nothing else it will help you assemble it with the spring later on. Practice makes it easier... one should hope.
"Seeing is not believing. Believing is seeing." -Judy the Elf