What version of Premiere Elements are you using and on what computer operating system is it running?
In the absence of that information, I will generalize, tending toward Premiere Elements 11....
a. Right click the Expert workspace Timeline video, select Fade from the pop up menu and then the wanted Fade Audio or Video command.
b. In version 11, you could click on Applied Effects/Applied Effects Palette/Opacity Panel and the shortcut Fades there.
c. You could keyframe the Opacity property in the Applied Effects Palette/Opacity or via the video track content rubberband at the Timeline Level.
Please supply more information for fading in out your video and audio track contents.
Add On...If you have Premiere Elements 11, you may be interested in the information on these Fades found in one of my blog posts