. As mentioned, you need to select the input that you'd like to record from and set the record levels. Also, make sure you select the proper hardware device profile from your system preferences (under sound).
The recording source could be the line in on your sound card or the mic jack on your sound card or even an audio stream that's being played back via a multimedia application.
(GUI for jack) is a really good idea. Jack provides you the most routing flexibility when recording digital or midi audio.
If you are really serious about digital recording in Fedora, I highly recommend using the low latency kernel provided by Planet CCRMA
, along with their comprehensive repositories of audio applications. (Btw - I recommend using F14 and skipping F15).