Windows Server 2012
1. Press Winkey+X, y (System), select Windows Update (bottom of left panel)
2. In the left pane, click Check for updates, and then wait while Windows looks for the latest updates for your computer.
3. If any updates are found, click Install updates.
Continue with below steps to enable Auto Update.
4. Change Setting and turn on "Install updates automatically" mode.
Windows Server 2016
1. Click on the ‘Start’ menu and select ‘All Programs’ then select ‘Windows Update’
3. Click ‘Check for updates’ and then wait while Windows looks for the latest updates for your computer.
4. If any updates are found, click Install updates.