It should be attached to the same bundle that the other connector comes from. The wire should be at least as thick as a pencil and terminated in a ring connector. You'll need the nut that fastens the wire on too. I don't see it in your picture.
The picture was just to show what part I was talking about. My car just died on me the other day and after taking a look at it (the alternator) I noticed that there's nothing going to that stub.
I found a wire that's bundled up with the 2 wires that plug into the alternator. It has a female end bullet connector on the end of it. Should I just try to put this wire there?