heya, you would connect your speakers up to your amp like you would your dvd player.
you would then use a Y splinter (red and white, left and right) from your front audio into your front input amp. and then do the same for the back connection, using a Y splinter again.
You would tehn select 5.1sound on your amp, and there u go... o and make sure windows is configured for 5.1 sound in control panel.
//looking at your screenshot again, u need to get 2 Y splinters, or can u use that wire u have at the moment, but u need to get an adaptor which goes from 2 to 1. the opposite connections of a normal Y splinter. if u get me?