Make sure your playback and recording device are set. If you’re going to record a stereo signal, set the number of channels to record to 2 (Stereo) on the Audio I/O preferences.
When picking a device to record from, make sure you’ve set up all the connections properly, such as plugging a microphone in to the Mic Input, and any other device in to the Line In of your sound card. Then check that the gain level knob(the amount by how much the input should be amplified) of the mixer of your soundcard is set right.
Since most soundcards can mix the inputs back in to the outputs, the easiest way to test your microphone is to speak in to it while playing with your sound card mixer. The sound card mixer is a piece of software either provided by the sound card maker, or by the operating system you’re using. The Windows mixer is pretty straight forward, though some soundcards bring their own along. The Mac’s mixer is controlled via the Sound Control Panel, and the Linux users have a variety of mixer applications at their disposal. Just make sure they work before yelling at your screen that nothing works.
Click on the red Record button to begin recording.
Click on the blue Pause button to pause the recording. Press it again to continue.
Click on the yellow Stop button to cease recording. The cursor will return to its previous position, before the recording was started.