Slide the barrel over the cable from the side, then pull tight, it will stop as it's funnel shaped.
This is how to wire it, I posted it earlier.
You'll have three wires capped at one spot, three wires capped at one spot, and the white does nothing.
:::::WIRING GUIDE :::::
Okay, first we will take note of our wires.
NOTE: Different brands tend to use different colors for some wires, so use the process of elimination to determine what color a wire is if it is not stated here.
*Kill Switch Wires : Green Wire & Red/Yellow Wire.
*Engine Wires : Blue Wire & Black Wire & White Wire.
*CDI Wires: Blue Wire & Black Wire.
*Other Stuff: Wire Cap
Now that you know what wires you have, it's time to connect them.
1. Engine's Blue Wire to CDI's Blue Wire.
2. Engine's Black Wire to CDI's Black Wire.
3. Kill Switch's Green Wire to Engine's & CDI's Black Wire.
4. Kill Switch's Red/Yellow Wire to Engine's & CDI's Blue Wire.
5. Engine's White Wire to Wire Cap.
Go ahead and fire up your bike real quick so you can test your brand new fully functional kill switch!
I don't know why the instruction manuals tell you to connect the white wire from the engine into the circuit. That's the ~7V live wire intended to be used by extra bike devices, like lights and such and such. When that white wire is in the circuit, the kill switch will not be able to stop the motor.