You add hops to the BK as you begin your sparge. The hops are in the wort during sparge (before the boil) and then remain throughout the boil. I've made a few IPA's that had FWH and they turned out great. I've never tried the same recipe without the FWH to see what the difference is. I guess the idea is that you get max bitterness from them.
Give it a try and see what you think.
Conical : bohemian pils
Keg 1: Brown Ale__Keg 2: Hellas
Keg 3: Hellas__Keg 4: air
Keg 5: AIR 6: Edworts Apflewien
My HERMS rig