To install drop the .pak file into the same folder as your MHRise.exe changing the "x" and "y" in the mod files name
so that there are no conflicts with other mods. If you have no other mods change them both to 0.

For example re_chunk_00x.pak.patch_00y.pak
Would become re_chunk_000.pak.patch_000.pak 0 if it was your 0th mod

To install via Fluffy Manager 5000 drop the mod file into the directory for Rise mods
It should look like this Fluffy Manager 5000\Games\MHRISE\Mods\[Mod Folder Name Here]\natives...
Then make sure to refresh mods and activate the mod in Fluffy Manager 5000

You only have to install via one of the methods above.