First of all, my apologies for my bad english.
I dit recently that stuff. I explain you how i did it.
Well, in my build.xml i created the next task
<!-- Run the Acceptance Tests -->
<target name="tests-aceptacion">
<junit printsummary="on" haltonfailure="yes">
<sysproperty key="concordion.output.dir" value="${test.accept.report.dir}"/>
<classpath refid="junit.class.path" />
<classpath>
<pathelement location="${build.test.accept.dir}"/>
</classpath>
<formatter type="xml" />
<formatter type="plain" />
<batchtest todir="${test.accept.report.dir}">
<fileset dir="${test.accept.dir}">
<include name="**/EspecificacionesFixture.java" />
</fileset>
</batchtest>
</junit>
</target>
With this task, i execute my EspecificacionesFixture class, that is the parent class of all my specifications, so it executes all specifications, and the outputs is left in ${test.accept.report.dir} folder.
Then, in Jenkins, you must download the HTML Publisher plugin, and then you must configure it correctly in your Jenkins task.
You can view the next link for configure it correctly
http://blog.shinetech.com/2014/05/09/concordion-integration-with-jenkins/
I hope it can help you.