Make a copy of your mix expressly for editing. While digital editing is non-destructive and reversible, working on a single stereo track simplifies the process. Keep separate mix files using descriptive names ("mysong mix 01 no reverb.cwp" for example) to avoid confusion when you make multiple mixes.
Set marker points for your edit using Track View, the default view in Sonar LE. Play through the song and press "F11" to drop markers at the points where you want to make edits. These do not need to be precise at this point.
Expand the Track view to fill your screen with the waveform of the song. Click the "Maximize" button for the Track window, then click the "Zoom In Vertical" and "Zoom In Horizontal" buttons at the lower right of the upper track window and bottom right of the screen respectively, until you have a large and detailed view of the song's waveform.
Turn off the "Snap to Grid" feature from the upper left Track View menu, if it is on. Using your markers as a guide, proceed to your first edit point. Click on the point where you want your edit to begin and SONAR will drop a green line. Press "F9" to select the start point for your edit.
Click and drag the green arrow to the end of your edit on the Time Bar at the top of the Track View window. When the line is placed where you want it, press "F10" to set the end point. The section to be cut out is now grey compared to the rest of the track.
Press "CTRL-X" to open the Cut dialogue window. For edits of this type, select "Events in Tracks" and "Delete Hole." All other boxes should be unchecked. Click on "OK" and your edit is complete. Play it back immediately to verify that you selected the correct points. Save your file and proceed to your next edit.