I've looked online but I must admit I'm a little lost on how to do it. Can I use normal speaker wire to biwire? Or do I use channel 6&7 as the second lead? Any thoughts?
Think of it as wiring your tweeters as entirely separate speakers from your woofers. So the positive and negative leads from the left front got to, say, the woofer, and the positive and negative leads from channel 7 or 8 (whichever is left) go to the tweeter. DON'T cross the wires - - don't have the positive leg of the front left channel returning to the negative leg of channel 7 or 8.
as mentioned above, just make sure you remove the links between the sppeaking binding posts. then just grab 2 runs of cable for each speaker, or 1 run of bi-wire cable.
I have the the front 2 channels powering the woofers and the extra 2 channels powering the tweeters.
finally once its all setup just turn on the bi-amp bit in the menu, simple