// In the Initialize Component Method you'll need to add this line
this.WebBrowser.DocumentComplete += 
     new AxSHDocVw.DWebBrowserEvents2_DocumentCompleteEventHandler
     (this.WebBrowser_DocumentComplete);


// in the WebBrowser_DocumentComplete Method you add:
// Get the Document Element
this.htmlDoc = (HTMLDocumentClass)WebBrowser.Document;

// Get a referrence to the UserName Text Box
HTMLInputElement txtUserName = 
     (HTMLInputElement)this.htmlDoc.all.item("txtUserName",0);
txtUserName.value = ConfigurationSettings.AppSettings["UserName"];

// Get a referrence to the Password Text Box
HTMLInputElement txtPassword = (HTMLInputElement)this.htmlDoc.all.item("txtPassword",0);
txtPassword.value = ConfigurationSettings.AppSettings["Password"];

// get the html button next 
HTMLInputElement buttonLogin = (HTMLInputElement)this.htmlDoc.all.item("btnSubmit",0);

btnSubmit.click();