In Elliptic Curve Addition, where does the second point come from?
In elliptic curve cryptography, participants need to agree on certain parameters. For example, you need to agree on which curve to use.

One of those parameters is called the base point generator, it is a point on the curve.


  You do EC multiplication with the private key to get the public key


Correct, PubKey = PrivKey*G = G+G+G+... PrivKey times where G is the agreed-upon generator. Does this clarify things?

You can see its definition in SEC 2 in section 2.7.1.