How do I get sound inputs to show up other than the built-in microphone?

I recently purchased a MacBook Pro. I have used Macs before to record audio, so I'm not an absolute idiot when it comes to Macs and audio inputs. However, with my new MacBook, no matter what I do, the only input that ever shows up in the sound options is the built-in microphone, even when devices are plugged into the audio port. Any ideas?