If you need to figure out which server is the WSUS (Windows Server Update Services) server or you need to know if the computer you are working on is pointing to a particular WSUS server, you need to know where the WSUS registry key is.
The WSUS Registry Key is:
HKEY_LOCAL_MACHINE > Software > Policies > Microsoft > Windows > WindowsUpdate
What are the Possible WSUS Registry Values?
AcceptTrustedPublisherCerts Reg_DWORD Range = 1|0
1 = Enabled. The WSUS server will distribute signed third-party updates if available.
0 = Disabled. The WSUS server will not distribute third-party updates.
ElevateNonAdmins Reg_DWORD Range = 1|0
1 = Users in the Users security group are allowed to approve or disapprove updates.
0 = Only users in the Administrators user group can approve or disapprove updates.
Name of the computer group to which the computer belongs, used to implement client-side targeting (for example, “TestServers.”) This policy is paired with TargetGroupEnabled.
TargetGroupEnabled Reg_DWORD Range = 1|0
1 = Use client-side targeting.
0 = Do not use client-side targeting. This policy is paired with TargetGroup.
HTTP(S) URL of the WSUS server used by Automatic Updates and (by default) API callers. This policy is paired with WUStatusServer; both must be set to the same value in order for them to be valid.
The HTTP(S) URL of the server to which reporting information will be sent for client computers that use the WSUS server configured by the WUServer key. This policy is paired with WUServer; both must be set to the same value in order for them to be valid.
DisableWindowsUpdateAccess Reg_DWORD Range = 1|0
1 = Disables access to Windows Update.
0 = Enables access to Windows Update.
If you want to automatically update there are many additional registry entries that are detailed HERE.