If you cannot find schematic, your wiring is going to be dependent on your cuts in your reel discs.
Map out where the symbols index to, mark them as such (e.g. ch, or, be, pl, etc. -- in your case melons and bars) and that will be your cuts that you wire the reel boards to.
Start 3rd reel with 90 wire (grey) is feed wire to power through the reels.
91 wire should be 2nd coin played, and 9(0) whatever is 3rd. These are all selected by odds disc in top unit, and then run back down to power the reels for pays.
Unless you change your reel discs and reel strips, what you got is what you have to wire it up to.
Pays go in SERIES from 3rd reel to 2nd, to 1st and then with hot signals down to payboard. Generally that is.........