For use on Mil4 figures in both Poser and DS, the hair prop and fits/mats are in:
your poser library - Hair/AprilYSH
your poser library - Pose/AprilYSH/AprilNye
For use on Genesis in DS, the hair figure and mats are in:
your ds content - People/Genesis/Hair/AprilYSH
your ds content - People/Genesis/Hair/AprilYSH/Nye Presets
For use on Genesis in Poser, the hair figure and mats are in:
your poser companion library* - Figures/AprilYSH/AprilGenesis
your poser companion library* - Pose/AprilYSH/AprilNye **
* your poser companion files may have been installed in the same runtime as your poser library, it does not have to be separate.
** mats apply to the genesis and mil4 versions but fits are automatic/conforming on genesis, ie fits poses are needed for mil4 only.
Hope that helps