check the link below
MSDN Link
To add a Web reference to a project
1 In Solution Explorer, right-click the name of the project that you
want to add the service to, and then click Add Service Reference.The Add Service Reference dialog box appears.
2 In the Add Service Reference dialog box, click the Advanced button.
3 The Service Reference Settings dialog box appears.
4 In the Service Reference Settings dialog box, click Add Web
Reference.The Add Web Reference dialog box appears.