Here's the very basic bits of what must be done...

First you need to include a reference to a custom namespace that describes you custom elements in both the newsfeed, and the xsl, something like this will work:
 xmlns:custTags="http://www.mydomain.com"

In your news feed the elements are generate like this:
 <custTags:agent>Joe Blow1</custTags:agent>
 <custTags:direct>N/A </custTags:direct>
 <custTags:cell>(361) 111-1111</custTags:cell>
 <custTags:email>joeblow1@stx.rr.com</custTags:email>

Then, you reference them with the calls in the xsl like this:

  <xsl:value-of select='custTags:agent'/>
   <xsl:value-of select='custTags:direct'/> 
   <xsl:value-of select='custTags:cell'/>
    <xsl:value-of select='custTags:email'/>
 

Then, you can use the News Feed v3.x module to render it on a DNN site.  Note, this will not work using the News v4.x module.

So, a practical example...

First the xml (newsfeed)

<?xml version="1.0" encoding="utf-8"?>
<rss version="2"
 xmlns:custTags="http://www.mydomain.com"
 xmlns:dc="http://purl.org/dc/elements/1.1/" >
  <channel>
    <title>From the Home Office</title>
    <link>http://www.somewherevalid.com/</link>
    <description>Our Area Agents</description>
    <pubDate>Thu, 24 Feb 2005 21:53:00 GMT</pubDate>
    <lastBuildDate>Thu, 24 Feb 2005 21:53:00 GMT</lastBuildDate>
    <generator>HGWorks - HandCoded NewsWriter</generator>
    <ttl>1440</ttl>
<item>
 <title>NW Region Contacts</title>
    <description>NorthWest Region Agent</description>
 <link>http://www.somewherevalid.com</link>
 <dc:creator>Phil 'iwonder' Guerra</dc:creator>
 <custTags:agent>Joe Blow1</custTags:agent>
 <custTags:direct>N/A </custTags:direct>
 <custTags:cell>(361) 111-1111</custTags:cell>
 <custTags:email>joeblow1@stx.rr.com</custTags:email>
  <pubDate>Thu, 24 Feb 2005 21:53:00 GMT</pubDate>
</item>
<item>
 <title>NE Region Contacts</title>
  <description>NorthEast Region Agent</description>
 <link>http://www.somewherevalid.com</link>
 <dc:creator>Phil 'iwonder' Guerra</dc:creator>
 <custTags:agent>Joe Blow2</custTags:agent>
 <custTags:direct>N/A</custTags:direct>
 <custTags:cell>(361) 222-2222</custTags:cell>
 <custTags:email>joeblow2@stx.rr.com</custTags:email>
  <pubDate>Thu, 24 Feb 2005 21:53:00 GMT</pubDate>
</item>
<item>
 <title>SW Region Contacts</title>
    <description>SouthWest Region Agent</description>
 <link>http://www.somewherevalid.com</link>
 <dc:creator>Phil 'iwonder' Guerra</dc:creator>
 <custTags:agent>Joe Blow3</custTags:agent>
 <custTags:direct>N/A</custTags:direct>
 <custTags:cell>(361) 333-3333</custTags:cell>
 <custTags:email>joeblow3@stx.rr.com</custTags:email>
  <pubDate>Thu, 24 Feb 2005 21:53:00 GMT</pubDate>
</item>
  </channel>
</rss>

And the XSL file...

<?xml version='1.0' encoding='UTF-8'?>
<!-- Using Custom Namespace Tags -->
<!-- Phil 'iwonder' Guerra -->
<!-- 2009-02-21 -->
<!-- Version v1.0 -->
<xsl:stylesheet
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 xmlns:dc="http://purl.org/dc/elements/1.1/"
 xmlns:custTags="http://www.mydomain.com"
 version="1.0">
<xsl:template match='/rss'>
 <xsl:value-of select='channel/title'/>
 <hr/>
 <table BORDER="1" CELLPADDING="3" CELLSPACING="1"  >
 <th>Region</th>
 <th>Agent </th>
 <th>Direct</th>
 <th>Cell  </th>
 <th>Email </th>
 <xsl:apply-templates select='channel/item' />
 </table>
</xsl:template>
<xsl:template match='item'>
<xsl:variable name="emailLink" select="custTags:email"/>
 <tr>
  <td >
   <xsl:value-of select='description' disable-output-escaping='yes' />
  </td>
  <td>
   <xsl:value-of select='custTags:agent'/>
  </td>
  <td>
   <xsl:value-of select='custTags:direct'/> 
  </td>
  <td>
   <xsl:value-of select='custTags:cell'/>
  </td>
  <td>
   <a href="{$emailLink}">
    <xsl:value-of select='custTags:email'/></a>
  </td>
 </tr>
</xsl:template>
</xsl:stylesheet>

I create the newsfeed and xsl using a simple text editor then upload it to my DNN site, and use the DNN News v3.0.1 module specifing the xml file for the source, and the xsl file for the xsl to render it.

With DNNv8.0.4 I get output like this:

From the Home Office