Rawhide welcome, since it's a pre carved, you need to start with the lock first, then work on the barrel. Most use use chisels, knives, and scrapers to inlet the barrel. If you don't have one of the building books, or even two, you should get them, or some of the building dvd's might help you. The lock needs to be fit first so you can determine the barrel touchhole in relation to the pan, or in percussion the lock to the drum.
Bill