You have a number of options. The goal is to create a short and engaging video showing off the salient characteristics of your project.
Take the resulting (short) video file and put it into your Portfolio folder.
Now you have a file. To play it back, I recommend using VLC Player, Windows Media Player, or similar.
To edit this file, you may use Windows Movie Maker in "All Programs" under the Start menu. Here is a decent short video on how to do this. Of course,
there are many other sites covering how to use this Microsoft tool, though Movie Maker is no longer supported.
More fully-featured is Adobe Premiere Pro as part of the CS6 package.
Basic editing would involve removing the "bumpers," the bits at the start and end of you clip which may simply show an empty screen or other unwanted
graphics. Slightly more advanced editing might include snipping out central sections of no interest.