If the button is not there, then you need to make sure that you’ve pre-ordered the game. You should know that buying Starfield once will get you access to it from both your PC and Xbox. So you don’t have to buy it separately for each platform.
Starfield was announced more than 2 years ago, and the game has been anticipated ever since. Initially considered for a 2022 release, Starfield will be out next month, in September, on Microsoft Windows devices and Xbox. The game is a Microsoft exclusive, and it the Redmond-based tech giant wants it to be the next big title in the gaming industry.
Truth is, from a hardware point of view, Starfield is already big: you’ll need 125 GB of free data to pre-install Starfield on your devices. Plus, future patches and updates might require even more space, so get ready to free some of your hard-drives.