Windows 8 computers update automatically using the Windows Update service, requiring no action on the part of the user. However, you may need to configure Windows Update for the first time if the computer hasn't updated previously.
To configure Windows Update, open the Settings menu, select Change PC Settings, and choose Update and Recovery. Next, select Choose How Updates Get Installed, choose Automatic Updates for the Important Updates prompt, and choose the option Give Me Recommended Updates the Same Way I Receive Important Updates. The PC uses these settings to automatically scan for updates, download updates when they are available, and prompt you to install the updates if applicable.