Put the unzipped folder into:

X:\Users\[user name]\Saved Games\DCS\Liveries\FA-18C_hornet\
or
X:\Users\[user name]\Saved Games\DCS.openalpha\Liveries\FA-18C_hornet\
or
X:\Users\[user name]\Saved Games\DCS.openbeta\Liveries\FA-18C_hornet\