BACKUP FILES BEFORE INSTALLING

Install weapons:
Run OpenIV > pc > models > cdimages > weapons.img > enter Edit mode and drag/drop files from the provided weapons folder into weapons.img

Install cutprops (for cutscenes)
Run OpenIV > pc > anim > cutprops.img > enter Edit mode and drag/drop files from the provided cutprops folder into cutprops.img

Install WeaponsInfo (OPTIONAL):
GTAIV > common > data > replace WeaponsInfo.xml with the provided file