Step 1: get as copy of the factory service manual from the home page of this forum.
Step 2: find the section on the charging and battery.
Step 3: start at the alternator end and test everything back to the battery. Look for burnt connectors, broken or blown fuses, loose connections.
Step 4: get back to us with what you found, if you weren't able to find a problem. :-)
We're here to help.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.