Source: Windows Central
Quick note: The new feature update will download and begin to install automatically. However, if it is not offered to you automatically, under the Feature update to Windows 10, version 21H1 section, click the
Download and install option to trigger the upgrade.
Click the
Restart now button.
Once you complete the steps, the May 2021 Update (build 19043.928, 19043.964, or higher) will install on the device. If you already had version 20H2 or 2004, the installation process will take only a few minutes because the system will need to download only an enablement package to switch versions. However, if you plan to upgrade from version 1909 or an older release, you can still install version 21H1, but the process will require full reinstallation.