If you want to shoot a Starr, BEST have it checked over by a competent person. Then seek-out an experienced breech-loading black powder paper cartridge shooter, presuming it's paper cartridge. Should your Starr be chambered for Spencer brass cartridges, Dixie Gun Works sells (or sold) cartridges using .22 blanks as primers. Presuming it's percussion, you can get away with a minimum: you'll need FFg black powder, musket-size percussion caps, and bullets. The bullets Starr likes are those intended for the Burnside carbine, sold by S&S Firearms. Simplest way to fire just a few shots are: grease the bullet with, say, a little Crisco, insert it into the carbine's chamber, point the muzzle down, fill the chamber with powder, close the chamber, put the percussion cap on the nipple, aim and fire. This will be a maximum charge, but the Starr has a strong action.
You would really benefit from overlapping with an experienced shooter of such weapons. As recommended above, get on the North-South Skirmish Association forum, start a thread. Likely you'll find someone near you who can help. I shoot a percussion Starr, live in western North Carolina, and have buddies who do likewise. The Starr incurred a bad reputation during the Civil War because undersize Sharps ammunition was issued for it. With the right ammo, the Starr...uh...shines.