Want to to join the Office Insider Program? Office Insider is available on Windows 10, Windows 10 Mobile, Mac and Android.

Says Microsoft,

Office 2016 is rolling out around the world, and were already hard at work on the next wave of updates. Weve asked Office 365 Home, Personal, and University subscribers to help make the next Office even better by becoming an Office Insider. Its easy to join, just install the Office Insider build and get early access to the new Office innovations.
Visit Office.com here to sign-up and download.