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);