How to connect a 5.1 Speaker System to a Line-Out

Hi Friends,

I bought a new Creative 5.1 Speaker System, which has got 3 Inputs. One for Sub-Woofer, 1 for Right Speaker and 1 for Left Speaker / Rear Speaker. But in my On-Board sound card has a Line-Out, a Line-In and a Microphone audio connector like in the below picture.

*i33.tinypic.com/2uhbl84.jpg

how can I connect my 3 Inputs of 5.1 Speaker System to a Line-out. Please guide me.

Regards
Yoda