The following code illustrates how to create organization service proxy in Dynamics CRM :

First you have to install the  Microsoft.CrmSdk.XrmTooling.CoreAssembly  Nuget package

var connection = CrmConnection.Parse("Url=http://crm.contoso.com/xrmContoso; Domain=CONTOSO; Username=jsmith; Password=passcode;");
OrganizationService service = new OrganizationService(connection);