Make a SOAP / XML Request?

[tommyboy123x]

This is a topic I'm very unfamiliar with, however it seems easier than I'm making it out to be. Basically I'm logging into the site through an API and making a SOAP Request. I understand the basics but what I don't get is how to actually "run" the request

This is an affiliate API for a DirectTrack script

Below is the XML code (word choice?) used, however I just can't figure out how to run it or make the request to get the result.

<soapenv:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:soap="http://soapinterop.org/">
  <soapenv:Header/>
  <soapenv:Body>
     <soap:optionalInfo soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
        <client xsi:type="xsd:string">affiliate_site</client>
        <add_code xsi:type="xsd:string">username</add_code>
        <password xsi:type="xsd:string">password</password>
        <start_date xsi:type="xsd:string">2008-07-01</start_date>
        <end_date xsi:type="xsd:string">2008-07-22</end_date>
     </soap:optionalInfo>
  </soapenv:Body>
</soapenv:Envelope>

Any help is appreciated!

Tom