Connect Designer to SharePoint sites


I am trying to establish Designer connection to sharepoint site. I have added correct site URL, but when I try to test connection using sharepoint login username and password it shows me a Failed error message.

Error Message: 

Connection to SharePoint using Web Services:
Unable to connect to '' using SharePoint Web Services due to the following error:

The request failed with HTTP status 403: Forbidden.

System.Net.WebException: The request failed with HTTP status 403: Forbidden.
at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)
at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
at Quest.NSP.SharePoint.Webs.Webs.GetWeb(String webUrl)
at Quest.NSP.SharePoint.SharePointWebsWebService.GetWeb(Uri webUrl)
at Quest.NSP.SharePoint.RemoteSPWebWrapper.<GetDescription>b__0()
at Quest.NSP.SharePoint.RemoteSPWebWrapper.HandleException(Action action)
at Quest.NSP.SharePoint.RemoteSPWebWrapper.GetDescription()
at Quest.NSP.SharePoint.UI.TestConnectionsForm.TestSharePointConnection(Object testContext)

Validating SharePoint Client Web Services Support

Credentials used:

Can someone guide me how I can access the SharePoint site using Quest Designer?

Thank You