Windows 10 will automatically download the October 2018 Update on your eligible device if you've turned on automatic updates in Windows Update settings. When the update is ready, you'll be asked to pick a time to install it. After it's installed, your device will be running Windows 10, version 1809. (To check whether you're already running the version 1809 update, click View update history on the Windows Update settings page.) Also note the following:
If you want to install the update now, select Start > Settings > Update & Security > Windows Update , and then select Check for updates. If updates are available, install them.
If version 1809 isn't offered automatically through Check for updates, you can get it manually through the Update Assistant.