it's very simple.
the "generic" informations and step-by-step is available here:
http://aluigi.org/about.htm#howusein the specific case of WS the following are some example commands:
listing all the files in one archive:
worldshiftext.exe -l c:\worldshift\data\textures.xe none
extracting all the files in c:\output_folder
worldshiftext.exe c:\worldshift\data\textures.xe c:\output_folder
extracting only the dds files
worldshiftext.exe -f "*.dds" c:\worldshift\data\textures.xe c:\output_folder