how do you jailbreak iPhone 3gs 4.0.2

I'm not even sure if it's possible yet, however, I figured I would ask, does anyone know how to do this?

PS. I have NO prior experience to this whole jailbreaking experience. So if it is possible please explain it in a more simple way.

 

There is a version of pwnagetool with a custom firmware bundle to creak a custom IPSW for 3gs, but this requires you to have a mac, a 3gs with old bootrom and already be jailbroken on 4.0.1 or below, but not with spirit or jailbreak me.

 

4.1 is releasing soon and the beta has already been cracked so there's no use to bother with 4.0.2.