The open beta is set to begin on Wednesday, February 21st, beginning around midnight PST. You can only participate in the open beta on Xbox Series X|S if you are a new player. In order to participate in the trial, you will have to link your Square Enix account with your Xbox account. If you already have a copy of Final Fantasy XIV on a different platform, whether that’s the free trial or a full license, you will not be able to participate in the open beta.
If you’re completely new to Final Fantasy XIV though, and you are on Xbox, you will be able to adjust your settings and download the Free Trial version and begin your adventures on the 21st. When the team announces the full launch date, they will also have an opportunity to transfer your data from the open beta version to the full launch.