No speakers NEED to be bi-wired. It is just offered as an option. It also comes in handy for people wanting to Bi-amp.
To correctly bi-wire speakers you take two sets of speaker cables. Connect them both up to your ampliifier and take one set for the top posts and the other set of cables to the lower posts. At the amplifier end you just connect both pairs of cables up to the same place exactly like you would with only one set of speaker cables.
Also, you take the connecting strap off of the speaker posts as they arent needed in bi-wire configuration.
Honestly, I wouldnt bother with it myself. I have tried it and did not hear any differences. And while I do think there is a difference between bi-wire and single wire setups when you are talking technical electronics stuff, I still dont think those differences add up to something you can hear.