I have to change my previous post but don't panic. The change is simple forget the scenery bit. You open the British Weapons Pack in your main FSX folders. Open that and there are folders to copy to simobjects folder. NOT SCENERY! Do the same for US Weapons Pack and go drop some bombs! The effects are not true representations of type of weapons explosions but they do go BOOM!
I hope I've helped more than I harmed. It's a way of life ;)