Since electrical is your weak point this might not be a good idea but....
The key switch has a 4 wire harness that has a red/w wire that should be +12 volts. It connects directly back to the battery.
When the key switch is on it connects the 12 volts to the brown wire.
No 12 volts on the brown wire = NO electrical action on the bike.
The other 2 wires black and black/w short the CDI to ground when the switch is off.