maybe you should be more specific on what exactly you try to achieve. Do you want to create SOAP based or REST webservices? Do you prefer a specific webservices library? You can even emulate (very simple) webservices with plain Servlets. What have you already tried? Where do you have problems?
Common libraries you could use are for example Metro, Jersey or Apache Axis. And there are surely many manuals online available on how to set up these famous libraries with Tomcat