You use a "Contact Report", where your crew has identified several ships in a group (you'll see the notifications in the text box), you lock-on to one of them, and send a "Contact Report". You have to be close enough to "see" them, yet not so close that they can see you. If there is a CV group, or a land-based air group, close enough to your location, you'll see them, generally no sooner than about 15-20 minutes, usually longer. You'll notice that skirich mentioned coming up to 30 feet, and you might get one out at PD, but usually radar depth is better (42-47 feet), or on the surface...
