Okay then, it is what I think it is them. Like I said, I have a 6.1 system so it won't be exact but ont he back of my sound card there are three slots for inserting the plugs. Each slot takes a set of speakers and subwoofer. It took a bit of playing around to get the right plug in the right slot. Sometimes the speaker plugs and the slots are color coded, sometimes not.
If they are you want to match color with color. If not you will need to play around a little bit. Also I am sure you checked that the onboard sound is capable for 5.1 speakers, right?