Sound Sculptor II deals with selections in two ways.  Track selection and selection points.  You can tell if a track is selected by looking at the track number 
on the Controls palette.  To toggle track selection hold down the option key and click on the track or press the track number on the Controls palette.  To select all of the tracks, click on a track with the control key down.  Selection points are made by clicking on a track and dragging to the left or right.  To adjust the selection points, hold down the shift key and click on a track and drag.

When editing sounds, if no part of the sound is selected and the track is selected, the entire sound will be modified, otherwise only the selected portion of the sound will be modified.