In this video, Gary from MacMost demonstrates how to use GarageBand to edit audio. He creates an empty GarageBand project,and then imports an audio file by dragging it in. He demonstrates how to move to any point within the audio file and view the waveform. To edit out a part, he moves the marker to the place he wants to split it,and then chooses "Split" from the Edit menu. He can also delete the section from the audio region editor. He shows how to select an area by dragging over it, and then delete or move it. He adjusts the volume by selecting points and dragging them up or down. To modify the sound, he goes to the Track menu, chooses Info, and uses the filters. When you're done, go to the Share menu and export the file. This is a good instructional video for learning how to use GarageBand to edit existing audio files.