Sheesh, the problem here is that I'm pretty sure EVERYONE is right. BUT, there are two kind of kill switches, normally open (NO) or normally closed (NC).
The best one to have for a blaster would be NO, this kind closes the circuit when you pull the lanyard. It can be hooked up parallel to the key switch, or one side to the blk/wht wire (key switch or thumb switch, same wire) at any point in the circuit and the other wire to ground. Essentially, you are grounding the CDI just like the key switch does. (I've been told that grounding the orange wire works too, but I KNOW the blk/wht does)
The other kind is NC and you can put it in series (cut wire and put switch in between) with something on the stator side of the CDI. On mine that is white wire with a red stripe (wht/red).
I just did both kinds about two days ago so this is really fresh in my mind...lol
To find out which kind you have check for continuity in the normal (tether inserted) position or maybe you'll get lucky and it will say on the package. NC will flow in the normal position.