Select Preferences - then turn on Advance Tools.
Then take a segment of video of Picture from your Events Library, and place it over a Picture or Video segment in your Project. When you lay the segment on top of the other one, it will open a options box asking what you want to do with these two segments. Picture in Picture or Side By Side. You can move the box to anywhere, or enlarge the size of the Pic n Pic. You can set it up to Dissolve in, or Zoom in, or Swap the two segments. With the Side By Side option......the segment that you have placed on top, will slide in and show both Side by Side.
There is a pretty cool app, called Tutor for iMovie - cost $4.99. I have it loaded onto my iPad.......it has 30 some short 3 or 4 minute video segments showing how to use all of the tools in iMovie.
http://itunes.apple.com/us/app/tutor-for-imovie-11/id416624070?mt=12
After the Banquet this weekend, I will see about making an up-load to YouTube.
Joe