https://www.gamespot.com/articles/sea-of-thieves-beta-now-available-to-pre-load-on-x/1100-6456291/

The closed beta for Microsoft's upcoming pirate game, Sea of Thieves, is set to begin tomorrow, January 24, and players can now start preparing for it ahead of time. The beta is available to pre-load on both Xbox One and PC, though only certain players will be able to participate in it.

Like the Sea of Thieves technical alpha back in December, tomorrow's beta is restricted to those who either joined the Sea of Thieves Insider Program prior to December 1, 2017 or have pre-ordered the title. Xbox One players who reserved Sea of Thieves digitally from the Xbox Store will find the beta waiting in the My Games and Apps section of their console's dashboard, while those who pre-ordered the game on PC via the Microsoft Store will find it in their Library. If you reserved the game at retail, you'll need to redeem the code you received for the Black Dog cosmetic pack on the Microsoft Store (PC) or Xbox Store (Xbox One) before installing the beta. You can read more about how to install the beta on the official Sea of Thieves website.