This is a simple procedure, but it took me long time to figure out how to do it because I couldn't find any instructions. So, here they are:
A) Click on Project in the main menu, then click on Add Clip, then on the source-file of interest, which then becomes known as a "clip."
B) Play the clip in the CLIP monitor (not the Project monitor) and pause the clip at the beginning of the segment to be extracted. (You can also simply drag the current-position marker under the clip monitor to the start-point of the segment.) If you're trying to extract a short segment from a long video, you might have to extract a segment, and then extract a segment from the segment, to get a sufficient degree of precision.
C) Click on the "left-arrow" button on the left in the row of buttons under the clip monitor. This marks the beginning of the segment or "zone" to be extracted.
E) Somehow get the aforementioned current-position marker to the end of the zone of interest (play the clip and pause it, or pause the clip and drag the marker), and then click on the "right-arrow" button next to the aforementioned left-arrow button to mark the end of the zone to be extracted.
F) Right-click on the display-area of the clip monitor and select "Extract Zone" in the menu which appears.
G) The rest should be obvious.
