Before you can edit, you have to select the fragment you need. You can do this by dragging the mouse over the desired part. The selected part will be a darker blue compared to the rest of the recording.
To listen to the selected audio clip you can press play on the ‘Transport toolbar or you can push the space bar on your keyboard. If you have to be very precise in your selection (and this is often the case when audio is concerned) it will be interesting to zoom in. To do this click the zoom function in the Edit toolbar.
In this Edit toolbar you will find the basic operations for sound editing like cut, copy and paste (first three buttons). It’s no problem whatsoever to cut a clip from one audio track and then to paste it into another track. With the 4th button you delete all sound outside the selection, with the 5th button you silence the selection.