I suggest to always install add-on mods into your mods folder and not into game files.

Installation:

1 - Move "fh16" folder with its content to [Grand Theft Auto V folder]\mods\update\x64\dlcpacks\

2 - Add the following line to dlclist.xml located in \mods\update\update.rpf\common\data\

<Item>dlcpacks:/fh16/</Item>

ENYOW :)