Hi, i'm new here and hope im posting this in the right place :-)

Im designing a website, which uses NGP products, which are for political campaigns to get contributions, newsletter signups and volunteers. For most of that stuff i can link to pages on their server. However, my client wants the splash page to have a simple newsletter signup form that feeds into the database. NPG has provided me with an API document to do this, and I have searched an search, but being inexperienced in coding, and more or a graphic designer, im at a loss. I created the basic form in dreamweaver, and was given the follwing information which i understand is XML, in order to do this. Im hoping somebody can guide me toward how a total newbie like me can do this, and not go crazy! You have no idea how much I would appreciate some help with this!

EmailSignUp
For signing people up to a campaign email list, NGP provides an XML Web service. The Web method name is EmailSignUp
and it expects 5 parameters:
1. Credentials: an encrypted string (provided by us) used to authenticate and authorize the request data
2. LastName
3. FirstName
4. Email
5. Zip
2.3.1 HTTP-Post
If using a HTTP-Post, this should be the format of request:
POST /ngpservices/OnlineContribService.asmx HTTP/1.1
Host: 206.132.30.245
Content-Type: text/xml; charset=utf-8
Content-Length: length
SOAPAction: "http://ngpsoftware.com/NGP.Services.UI/OnlineContribService/EmailSignUp"
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<EmailSignUp xmlns="http://ngpsoftware.com/NGP.Services.UI/OnlineContribService">
<Credentials>{supplied by NGP}</Credentials>
<LastName />
<FirstName />
<Email />
<Zip />
</EmailSignUp >
</soap:Body>
</soap:Envelope>
HTTP/1.1 200 OK
Content-Type: text/xml; charset=utf-8
Content-Length: length