I know how to crossfade, but I did not find out, how I can fade out at the end of a mavie with the LE-Version. Help says that envelopes are not available with LE.
If you are just fading one event, drag on the upper-right corner of the event, towards the center of the event... you should see a fade-slope.
To fade a number of tracks, you can place generated black on a top track, art the point of the fade-out and fade to black dragging the upper-left corner of the generated black.