In a domain environment you can configure Automatic Updates by Using a Group Policy.
Edit your Group Policy
Computer Configuration\Administrative Templates\Windows Components\Windows Update\Configure Automatic Updates
Set “Configure Automatic Updates” to “Auto download and schedule the install”.
If you are not using group policy’s. Login to the computer with an administrative account and go to:
Control Panel\All Control Panel Items\Windows Update\Change settings.
Check the box to Allow all users to install updates on this computer, then select OK.