Provided your machine has a supported operating system (support for Windows 2000 has been dropped in version 10+ due to obsolescence) it should update automatically eventually as long as your subscription is current.
This process can be delayed if you obtain McAfee protection via your ISP or computer maker as they often modify the software to badge with their own logo and make other minor changes.
The fast way to obtain the latest version of the software is always to uninstall, run the MCPR cleanup tool (Useful Links at the top of this page), reboot and reinstall from your online account rather than any CD you may have.