As to location, it goes in the same place the big-shot microwave guys put their transverters: right at the feedpoint (or as close as you can get), so that the signal that's applied to the preamp has as high a signal-to-noise ratio as possible and is as high above the noise floor as possible.
As to
power, either DC supplied at the antenna site, or more commonly applied down the
coax. I imagine the DC would be directly applied to the
coax (or even better, low-passed onto it for good measure), and the RF would be capacitively-coupled onto the feedline, the end result being RF that's cleanly biased up 5 or 12 or whatever volts. For this to work, since it's biased onto an
unbalanced line, the
power supply should be really clean, though because it's an FM signal we're talking about, it's not as critical because there is no amplitude-modulation component to the signal.