I have just come in from my morning walk and found these really good explanatory websites which give more information on fitness walking with poles.
Nordic Walking with Fitness Walking Poles and this one is very good also:
Youtube walking poles - Ask.com YouTube Search. This second one is has a really good explanation of pole walking, but I could not separate it out from the search engine I was using, so scroll down until you see the video. There are a lot more videos available on pole walking, but these cover the basics.
If you have ever cross country skied this action will come naturally to you.