Microsoft will start the rollout of its Windows 10 Creators Update on April 11 but if you want you can already install this upgrade today. All you need to do is download the latest version of the Windows 10 Assistant, this will give you the option to install the Creators Update immediately.
The Creators Update itself is build 15063.0, but there will be a small Cumulative Update delivered on April 11. Previews of this patch have been rolled out to insiders, with the fast ring Insiders on 15063.14 and slow ring Insiders on 15063.13. Using the Update Assistant or Media Creation Tool appears to also update to 15063.13. This situation may well change by the actual release day next week.