I have never used bergamot in a brew, but I do know some things about it. The flavour comes from the peel of the Bergamot Orange, not to be confused with the other kind of bergamot, which is related to mint. It was sometimes used in beers in the middle ages (gruits), and I know right now it's used in a Belgian called Koyt. The flavour is a volatile oil, so it should be added at the end of the boil, or during secondary. As for how much to add, though, I have no idea. I would recommend just looking at how much orange or lemon people use, because they're so closely related.