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Go to this link https://support.microsoft.com/en-gb/help/4027667/windows-update-windows-10 and click the "Check for updates" button. You may get a pop up asking if you want to allow the link to open the settings app. Click Allow. This will open the Windows update menu.
Option 2:
Right click the start menu and click Settings
Then click Update & security in the settings window.
Once the settings app opens click Check for updates or Install Now
Windows 7
In Windows 7 go to Start > Control Panel > Windows update > Check for/Install updates.