XML Transforming

Hi,
I have a problem due to including the xalan.jar. When I write a xxx.xsl file (including this here -->
<xsl:stylesheet
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
), then "http://www.w3.org/1999/XSL/Transform" is written in red and a error message says that the uri is not registered. I tried to link it ( in Options/Ressources the http://www.w3.org/1999/XSL/Transform" to the xalan.jar )but this seems not to work. Can someone give me a short intro how I can transform a xsl + dtd + xml file with IntelliJ(PLEASE!!!) ? Some of my colleagues use NetBeans, and it is easy there to handle this task...besides all of my documents(xml, xsl, dtd are in the projectpath).