You have 2 options. The first is the least expensive:
Buy Ducati part number 97380382A and replace the stock headlight bezel. It has the tabs needed to attach the guard. I think the bezel has the screws to attach the guard. I do know you'll use the clamping bolt/nut from the stock bezel.
Option 2 is more expensive:
Buy Ducati part numbers 97380231A (billet bezel) and 97380391A (clamps). The clamps attach to the bezel and the guard attaches to the clamps. I know in this case the screws to attach the guard come with the clamps but, again, you'll reuse the clamping bolt/nut.