If you select particular sound clip on the timeline you will notice controls that allow you to add fades, adjust volume, adjust panning, and edit in/out points. To add fades simply drag the boxes at the top right or left hand corners of the sound clip. A yellow line will appear that reduces the volume of the clip along its slope. You will also notice buttons to adjust volume and panning i.e. spreading the sound signal into the left or right channel.
The in and out points basically crop the clip. If you hover your mouse at the edges of the clip, the points will appear automatically. You simple drag left or right to crop. The edit button will open the clip in zoomed view. This allows you to finely change certain elements of the waveform. Once you’re done with the edits you can return to the main window by clicking on back.