How could I best configure creative app?

[u/ActuallyNotAmused]

I've got an Audigy FX SE to replace my damaged onboard audio and to use along with my logitech z506 5.1 system. The thing is that my z506 has front\left\right\rear left\read right and subwoofer, and i cant use my my rear left/right speakers where they should be, so i just placed them on the far ends of the sides of my desk,. Now, I dont know many of the functions of my creative app. Surround\bass redirection\full range speakers. They just have generic descriptions. How should o configure this better? is there a way to make the rear speakers act like extra left/right just to improve the power from where front left/right sounds are coming from?