How do I invoke an SSL socket then send a standard POST request to that socket.

I am integrating a payment system from www.directone.com.au onto a clients site. This is the first payment system that I have done and for some things I have NO IDEA what they mean.

Their documentation says I must "invoke a SSL socket on port 443 and then send a standard POST or GET request to that socket. I have no idea what this means.

I've set up a dummy page to test my coding which you can find at http://www.numbers1.com/DirectOneProcess.aspx . My code for the button click is listed below. The return value is displayed on the page and from their documentation means that its a server error - meaning I have in some way supplied the wrong information. There's a few things I am keen to find out:

A: If I don't yet have an SSL certificate installed on the server - will that make a difference??
B: How do I invoke a SSL socket??
C: Am I even close with the code I've created??  and will I have to break down the returned string to get the values out or can I use some other peice of code -  ie: string sCode = request.form["summary_code"];

CODE BEHIND:
protected void btnProcess_Click(object sender, EventArgs e)
    {
        ProcessRequest();
    }
public void ProcessRequest()
    {
        DirectOneDB direct1 = new DirectOneDB();
        string TestingURL = direct1.TestingUrl;  //Gets the testingURL from the DirectOneDB class.
        string LiveURL = direct1.LiveURL;  //Gets the LiveURL from the DirectOneDB class.

        //Get page results
        string cNumber = txtNumber.Text;
        string cName = txtName.Text;
        string cExpiry = txtEMth.Text + txtEYr.Text;
        string cCCV = txtCCV.Text;
        string cAmount = lblAmount.Text;
        string cReference = lblRef.Text;

        //Add the string components - the url will be added later.
        string urlValues = "?vendor_name=*******&vendor_password=*****&card_type=AUTO&" +
            "card_number=" + cNumber + "&card_holder=" + cName + "&card_expiry=" + cExpiry + "&card_ccv=" +
            cCCV + "&payment_amount=" + cAmount + "&payment_reference=" + cReference;
               
        //Create the Web Request
        HttpWebRequest newRequest = (HttpWebRequest)
            WebRequest.Create(TestingURL);

        //Set the values for the web request
        newRequest.Method = "POST";
        newRequest.ContentType = "application/x-www-form-urlencoded";
        newRequest.ContentLength = urlValues.Length;

        //Write the Request String
        StreamWriter streamOut = new StreamWriter(newRequest.GetRequestStream(), System.Text.Encoding.ASCII);
        streamOut.Write(urlValues);
        streamOut.Close();

        //Send the request and get the response
        string directOneResponse;
        StreamReader streamIn = new StreamReader(newRequest.GetResponse().GetResponseStream());
        directOneResponse = streamIn.ReadToEnd();
        streamIn.Close();
       
        //Show the value returned on the page;
        lblStreamResponse.Text = directOneResponse;
    }

Thanks in advance for any and all help. Hope this doesn't sound too confusing but I wanted to get as far as I can myself.
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