jet fan control kit--water jacket plug???

ok people it says i have to take out the water jacket plug or something of that nature and replace it with this brass plug thathas a sensor attatched to it. I found the knock sensor and took that out--but its not the same size as this new brass piece. The directions say that its on the passenger side of the engine--which is where i found the knock sensor. Where the hell is this plug they are talking about?!?!? I have to get this fan control kit in, cuz im tired of wondering if the car is gonna over heat when im in traffic on a hot day.
Car is a 94 lt1 6 speed

I hate anti freeze

Dante