To select segments in an image, click down at one point of the image and drag to another point. The contained rectangle is the segment. You can then assign features to the segment using the Coding Pane.
To select a segment, click on the outer border of the segment (or use the '<' and '>' buttons).
To resize a segment, click down on the corner of the segment, and drag the corner where you want it to go.
The Toolbar provides 3 extra buttons: