Windows 10 May 2019 Update (version 1903) is already available to the seekers who manually checks for update and will gradually available to millions of other computers running Windows 10. If you are one of them, you will get the upgrade notification in coming weeks.
If you are looking for the Windows 10 May 2019 Update ISO image for offline installation, here's a quick trick by which you can download it directly from the Microsoft site for free.