Microsoft today announced the full availability of Windows 10 "April 2018 Update" for the stable branch of the OS. The official ISO images can be downloaded from the company's web site. Existing Windows 10 users can install it via Windows Update.
However, Windows Update won't install Windows 10 version 1803 automatically. You should manually check for updates to get it. Microsoft is going to roll out it via their automatic delivery service starting on May 8.
Windows 10 version 1803, now known as April 2018 Update, includes features like Timeline, Focus Assist, a brand new Xbox Game Bar, Dictation and text suggestions for the physical keyboard, etc. Its complete change log can be found here:
So, you can download the OS from the official Microsoft web site as described in the article Download Official Windows 10 ISO Images Directly Without Media Tool. If you prefer the Media Creation Tool method, it is described in detail here. It is an official tool, which also can be used to download the ISO image.
You might be interested in reading how to perform a clean install of Windows 10. See the following article for reference.
If you are not happy with this update, you can postpone it. Please refer to these posts:
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