How to install Scosche RLC Bass nob?

I bought a scosche rlc amplifier bass nob from sonic electronix a couple months ago but don't know how to install it. It says it installs to the RCA inputs and outputs but i have no clue where that is. is that in the back of the head unit. also if it is how would i install it? do i remove the head unit and then where would the cords run from. Confused and really want to install it because my subs overpower my speakers when i play a cd in my car, even when i turn down bass on the head unit all the way. Thanks a lot in advance.

I probably should add extra information even if its not necessary. the amp i have is a kenwood KAC 9104D and the car is a 2005 nissan altima 2.5 sHow to install Scosche RLC Bass nob?
first off i wouldnt use that at all. all it does is reduce your signal to noise ratio creating room for unwanted noise if i were u id turn the bass boost down on the amp its self i believe it 0 to 18 db gain and also turn the gain down the more ur gain is down the better ur sound quality will be also better for subs life span as well the more s/n ratio the less clipped notes which are hard on subs so like i said thats a in line resistor that only reduces signal which is 1 of the worst thing u can do so id do gain then boost and try to match gain level to deck out put level ps if ur amp is running with high level inputs then there are no rca so it wouldnt work ne way feel free to email me if u have any other quiestions or concerns