WBCCI is the Wally Byam Caravan CLub International, or the Airstream owner's club.
In order to join, you first must have an Airstream or Argosy travel trailer or motor home.
As far as lessons or classes, the best way to learn to tow and operate your trailer, would probably be to arrange for the seller to show you how everything works, and how to tow (and back up). A few trips around the neighborhood, and backing back into his driveway a few times should give you the general idea. This of course if they are willing and able to help you, and there is a location to do this.