What version of Premiere Elements are you using and on what computer operating system is it running?
For now I will assume Premiere Elements 12 Expert workspace on Windows 7, 8, or 8.1 64 bit to give you an idea of what should be involved....
Right click your video on Video Track 1, and, from the pop up menu, select either Rotate 90 Left or Rotate 90 Right.
Click on your Timeline Video to select it, then go to Applied Effects Tab/Applied Effects Palette/Motion Panel expanded where you
will find the Rotation feature there.
Please determine if either of the above works for you. If any problems, please give more details including naming the workspace of the Premiere Elements version that you are using.
Premiere Elements 11 or 12, Expert workspace or Quick workspace
Premiere Elements earlier than 11, Timeline workspace or Sceneline workspace