Q: How to wind the spool / spiral?
A: It doesn't matter (!). As long as you 'load' all the groves with both ends of the cable. Once you loaded them, put the spool halfway inside its housing and turn it with your fingers to see who it works. You'll see that as it releases cable on one side into the rails, it will pull in the same amount of cable from the other side. Once one end reaches the end of the cable, the spool will stop, naturally. Turn it the other way and it will stop on the other side. Meanwhile, the spool is always full of cable, either from one side, or the other, or half and half. End to end is exactly the distance that the window is moving up and down. You can't make it wrong as long as you don't leave on groove completely empty, and it doesn't matter from what side of the cable.
I suggest, that for practice and to see how it assemble without the tension, assemble everything without the spring, but with the black piece.
To my BEST recollection, when I assembled everything, the last piece I put in was the spool. I left the spool out, compressed the spring, and then pushed the spool into its place.
"Seeing is not believing. Believing is seeing." -Judy the Elf