Splice into this wire like so...
Now connect the molex connector from the wiring harness into your speedohealer.
At this point with the speedohealer connected and the ignition on, whenever the rear wheel turns the speedohealer's led should blink.
To make sure that it's running properly. Turn off the bike, then push lever one up into the ON position. Then turn on the ignition and on your speedometer it should show a constant speed. Mine went from 0 -> 6 -> 12mph. Your speedohealer is now properly connected and ready to be calibrated.