I believe that completing "Stop the Signal" might be a rumour or a left-over from beta. It seems that all 3 times i did it (i had forgotten/lost my first open beta key prior to my preorder one) it was level 6 that needed to be unlocked.
What might be happening is that players are leveling to or past level 6 and happen to have completed "Stop the Signal" so some people are thinking it goes hand in hand.
To confirm, when you log in the character selection screen you should have two options beneath your character screen, one to create a federation character and another to create a klingon. Good luck!