Audio Systems: amp, rca cables, female rca

Question
hi my question is since my amp has 4rca inputs (2red 2white) for front and rear and my stereo has only 2rca and right now i have the 2rca inputs for front connected but have no idea on how to connect the rear rca cables how do i connect the other 2 inputs on my amp or do i have to get the stereo wires modified

Answer
Please give me make and model numbers.  Without knowing the configuration of the exact product I can only guess what you have as not all models have the same I/O ports.

However, most amps that have 4 input jacks are 4 channel amps and drive two sets of speakers.  If your feeder amp has only stereo output you need a combiner so you can drive the fronts and rears with the same input.  (Some amps have a combining switch on the amp that will tie the two together).

You can split the outputs of the feeder amp/preamp using two of these:

https://www.cablesforless.com/p-129-mono-splitter-6-inch-female-rca-plug-to-2x-male-rca-plugs.aspx

They can be purchased at Radio Shack and many other such parts stores.  Even Walmart has them....