If you want your package to write to the real FileSystem instead of the virtual FileSystem, use Package Editor to change Isolation. You can change Isolation mode under the General tab, which is a global setting, or you can change Folder Isolation under the Files tab, which sets Isolation for individual folders. Please see here for documentation on Package Editor.
Tip: if you need to give Full access to a drive, Add empty folder and name it with the drive letter followed immediately by an underscore, e.g. F_