Instructions
Ask around in local gun shops for experts in antique weaponry.
Know exactly what kind of gun you have: style, year and manufacturer. The type of gun and the kind of parts it takes play a large factor in how to restore it.
Look on the Internet to find replacement parts. Many are very specific and difficult to find, so searching online is a better bet than looking locally.
Try to find replacement parts that are as close a fit as possible to the original. Exact replacement parts may not be available, but you may be able to find something similar.
Ask your firearms expert if he can teach you to restore your antique guns if you really want to learn how to do so yourself. Or ask if there is a class you can take that can train you safely in gun restoration.
Take a gun safety course. Even if they are old and worn out, firearms can be dangerous.
Learn how to clean your guns properly and safely. Regular cleaning will prevent them from falling into disrepair.