Step 1) Run the eclipse_project task.
this implies running the ant command as below -
C:\ptc\Windchill_10.0\Windchill>ant -f bin/tools.xml eclipse_project
It is basically creating a workspace and placing .classpath and .project filesin this workspace.
Further as the eclipse_project.help says, the newly created workspace and projects are used.
Hope this helps.
-Nitin