Note: For people who have the premium edition, it will just show up as "Starfield" in your steam library, but it is the premium edition. You can preload it, it's about 88gb, and you will have early access to the game
Second note: when the time comes, steam will unpack the encrypted files, so while you most likely don't need to download anything (I don't know if there's a day -5 patch), make sure you have at least 150gb total (before downloading) on your SSD.