inline converter, wiring, 1994 es300

My car-Lexus es300 year-1994 hi thansk for taking the time to read this, i am putting a inline converter on my old manufacture radio to get the signal threw to my amp which go to my subs But the main purpose of me making this is does any one know what wire i hook my inline converter up to. the instructions that came with it says connect IEC Auloc gray wire (+) and gray/black wire (-) to the right speaker out put of the source unit. Connect IEC AULOC white wire (+) and WHITE/ black wire (-) to the left speaker output of the source unit. i dont know what wire to connect these to my head units wires. ////this is also only to power my sub woofers my speakers are being run off another amp. Number one do you know what wires are what in my car? or where i could find it? Number two i have also heard rumors that they need to be connected to the back speaker wires? if that's true then i need to know what wires they are then. Thankschris

also if you know what wire i should hook my signal cable up to that would be appreciated too thanks againchris