I bought a Scosche Line output converter, where would I hook this up at?

I bought a Scosche Line output converter, where would I hook this up at? Would I take apart my dash, and attach it to the back of the head unit? Or, should I attach it to the rear speakers, where im going to hook up my 10" Pyle Bass tube, with the built in 500watt amp. if I hook it up at the rear speakers, would they shut down the rear speakers?

I need some help... Thanks in advance. you can reach me on aim..my sn is: Billabongsur



thanks again..I bought a Scosche Line output converter, where would I hook this up at?
you can hook it up at the rear speakers.. it wont shut down the speakers at all.