Noob XPath question

Hi,
Im a noob in this Xpath thing.
Can anyone help me how to ge XPath from this XML.
I need to map "article-field1" and "article-field2" to my custom field

 <title>Testing</title>
  <link>http://example.org</link>
  <description>Description</description>
  <language>en-us</language>
  <lastBuildDate>Mon, 13 Feb 2012 00:00:00 +0000</lastBuildDate>

  <item>
    <title>Title Here</title>
    <link>http://example.org/2012/03/27/</link>
    <description><![CDATA[
        <div id="article-field1"><a href="http://example.org/test1">Test 1</a></div>
        <div id="article-field2">123</div>
    <pubDate>Tue, 2 Mar 2012 00:00:00 +0000</pubDate>
  </item>

Thanks in advance!