So if I multiply the 62 numbers together, would that work?
But if I add them together , won't that create a very weak key, a small number that is still in the range of computers that go through addresses 1 by 1? So isn't it important to have the key at the higher ends of the randomness.
No, multiplying the numbers would destroy the informational entropy, you should string them together and take a hash of the string (SHA3-256 for example).