Weapon visibility in normal free flight is controlled by their weight, and the droppable weapons are only available by editing a saved flight.
Start FSX and load up the Beaufighter. You'll need to use either the Mk.VIc or Mk.X models as the VIf doesn't carry rockets or torpedoes.
From the FSX menu, click on "aircraft", then select "fuel and payload"
In the screen that appears, click the "change payload" button.
You will see two entries for rockets (port and starboard) and one for torpedo. These are followed by two numbers. These are the weights that have to be entered to get them to show. In the case of the torpedo, you will see "Torpedo 50/1610" If you enter 50 in the box next to this the torpedo cradle only will display. Entering 1610 will display both the cradle and the torpedo.
The same applies to the rockets, entering 50 will display the rocket rails only, entering 260 will display both the rails and rockets.
Click OK to return to the sim.
Thats the easy bit!
If you want to fire the weapons you will have to do a bit of editing of saved files.
Now you've (hopefully) got your weapons displayed, click "Flights" from the main menu, and click "save"
Give it a suitable name and click OK.
Now you have to find that saved file. It should be in the "Flight Simulator X Files" folder located in your "My Documents" folder.
Find the file you just saved. It should have a .FLT extension, i.e. "Beaufighter test flight.FLT"
Open that file in notepad and at the bottom add either:
[DroppableObjects.0]
ObjectSet.0=RP salvo, 1
or
[DroppableObjects.0]
ObjectSet.0=Torpedo, 1
You can't use both at the same time I'm afraid. That's a limitation with FSX.
Save the file.
Now load that saved flight. You should see a display on the top right of the screen with the weapon name and the number of items left.
To release the weapon, use the keypress for "release droppable objects". Mine is set for control-D, but I can't remember if that's the default setting. You may need to set it up in the controls menu.
