Installing a car audio system with factory oem/factory head-unit..Help!?

I'm trying to get a system installed in my 1995 Toyota Landcruiser. Here is the problem. I don't have a aftermarket headunit. I will probably look to upgrade this later but for now I need help installing my system without it. I bought a line output converter. I have the amp, subs and a capacitor. Can someone please let me know how I can install my amp (REM cable + RCA) to a factory head unit using the line output converter. Thanks!!!