You have a fair bit of work ahead of you before you shoot that gun or even start in on the task of gathering consumables for it.

Start out by ordering a brick of Cerrosafe chamber casting alloy from Brownells.
Get some pure lead roundballs greater in diameter than the barrel bores too.
Cast the chambers including an inch or so of the bores --both of them-- and slug both bores at the muzzle and at the chamber end.

From there you'll be able to tell what kind of cases the gun was set up for... they could have been paper or brass with thin or thick walls.
From the bore slugs you'll be able to tell what diameter of projectile to go with, that factored along with the rate of twist and the type of rifling profile and it's bore/groove measurements, and with some consideration of the proof marks, will get you pointed in the right direction in your search for cases, bullets, and what kind of load to set the gun up with.

Can't wait to see what you guys come up with.
I expect you'll have a bit of a learning curve to climb in the early stages, it'll likely be quite rewarding for you.

--Tinker