To insert values using webservices

Hi Iam having xml url like this and I want to insert parameter values using this webservices.

<service xmlns:atom="http://www.w3.org/2005/Atom" xmlns:app="http://www.w3.org/2007/app" xmlns="http://www.w3.org/2007/app" xml:base="http://www.xyz.com/">
<workspace>
<atom:title>Default</atom:title>
<collection href="register">
<atom:title>register</atom:title>

I have sent xml request like this

var xhr = Ti.Network.createHTTPClient({
    onload: function(e) {
 
         var doc = this.responseXML.documentElement,
            elements = doc.getElementsByTagName("collection");
 
                  elements.item(0).getAttribute("href");
                  Ti.API.info(elements.item(0).getAttribute("href"));
 
 
        alert('success');
    },
    onerror: function(e) {
 // this function is called when an error occurs, including a timeout
        Ti.API.debug(e.error);
        alert('error');
    },
    timeout:5000
});
xhr.open("POST","http://www.xyz.com");
 
// Set the content-type header
xhr.setRequestHeader("Content-Type", "application/xml; charset=utf-8");
 
xhr.send();  // request is actually sent with this statement

How can I insert values using this xml, do I need to get the parameters they have used for that register element. Will it work if I pass the parameters. Thanks