How do i install a new ignition barrel on my piaggio Nrg 2005 moped?

I purchased a used piaggio nrg 2005 moped today and the guy i purchased it off had lost his keys so he had purchased a new new barrel and never got round to fitting it.i need to get it fitted asap. At the moment there is just a hole there , it is wired up so you just press the button to start it , but that means anybody could steal it!!

need to know asap otherwise im afraid it will go walking!!