Configuring the Windows Update Client
By default, Windows computers, both the server and client version, download updates from Microsoft's Windows Update servers on the internet. In order to configure Windows hosts to take updates from an internal WSUS server, you need to update the configuration of the Windows Update Client that is built into Windows.
The easiest method of configuring the Windows Update Client is to use Group Policy. You create a Group Policy Object (GPO), configure the policy with server names, and so on, and then assign the policy.
You can apply a single GPO to the domain as a whole (configuring Windows Update Client on every domain-joined host) or apply policies at the site or OU level, depending on the complexity of your WSUS implementation. A small company located in a single site might apply just one policy at the domain level. Large multinational organizations may have multiple WSUS servers around the globe and might need multiple Windows Update policies applied...