HI,
How to read XML file:
https://social.msdn.microsoft.com/Forums/en-US/5dd7261b-86c4-4ca8-ba87-95196ef3ba50/need-to-display-xml-file-in-textboxes-edit-the-data-and-save-the-new-xml-file?forum=csharpgeneral
How to work with CRM:
ClientCredentials credentials = new ClientCredentials();
credentials.Windows.ClientCredential = new System.Net.NetworkCredential("USER", "Password", "Domain");
Uri uri = new Uri("http://server/Organization/XRMServices/2011/Organization.svc");
OrganizationServiceProxy proxy = new OrganizationServiceProxy(uri, null, credentials, null);
proxy.ServiceConfiguration.CurrentServiceEndpoint.Behaviors.Add(new ProxyTypesBehavior());
IOrganizationService service = (IOrganizationService)proxy;
//using "service" you can create, update and retrieve entities.
More information here about service functions:
https://msdn.microsoft.com/en-us/library/gg328198.aspx