I've updated to Windows 10 now so can't look back to see how it's done in earlier Windows. Bit I've searched on line and this is what I've found:
'To check for Windows updates
1. Open Windows Update by clicking the Start button Picture of the Start button. In the search box, type Update, and then, in the list of results, click Windows Update.
2.In the left pane, click Check for updates, and then wait while Windows looks for the latest updates for your computer.
3.If you see a message telling you that important updates are available, or telling you to review important updates, click the message to view and select the important updates to install.
4.In the list, click the important updates for more information. Select the check boxes for any updates that you want to install, and then click OK.
5.Click Install updates.
Read and accept the license terms, and then click Finish if the update requires it. Administrator permission required If you're prompted for an administrator password or confirmation, type the password or provide confirmation.'
Hope the above helps.