My 1980 350 corvette won't start. Can you, the people of fluther, help me?

1980 350 corvette. And I don’t know ANYTHING about cars.
I turn the key and it doesn’t even try to turn over. Doesn’t make a sound, doesn’t do ANYTHING. All signs point to battery failure, but I’m not sure. Is there any way to diagnose this? If it is the battery then what can I do? Any help you can give me would be greatly appreciated.