Buy a book:
http://www.amazon.com/gp/offer-listing/1893939995/ref=dp_olp_new?ie=UTF8&qid=1317736611&sr=1-1&condition=new (check for a pdf or mobi or kindle format if you have a kindle or ipad. Also view You Tube. www.youtube.com/watch?v=0bazkLeY6b4 a and view www.wireshark.org/news/20060714.html and view
https://blog.wireshark.org/2012/10/wireshark-tutorial-series/ . Also, go to www.sans.org and view GCIA (intrusion analysis) and read the papers on wireshark. Next, go through what the video showed you and try to do the examples in the book. The very best way to learn wire shark is to play with it. Good luck.