Simply copy the unzipped Gulfstream V folder and all of the subfolders to your SimObjects folder in FSX. Then enter the EFFECTS folder and read the effects.txt file for smoke installation.
Flying:
The only real thing to note with this aircraft (in FSX) is that the flaps are extreme, and the engines are powerful. No more that 2 notches are needed for take-off or landing with flaps. Rolling with less than 70% fuel will require no power, and some braking.
