The Openfire server has a single configuration file called openfire.xml and located under the exo-openfire/conf directory. Configuration is based on properties expressed in an XML syntax. For example, to set the property prop.name.is.blah=value, you would write this xml snippet:

<prop>

  <name>

    <is>

      <blah>value</blah>

    </is>

  </name>

</prop>

Openfire has an extensive list of configuration properties. You can read a list of all properties on this page: http://www.igniterealtime.org/community/docs/DOC-1061.