As you most likely know by now, Windows 8.1 Preview will be available as a free update from the Windows Store, but some new leaked details provide an in-depth look at the entire process.It appears that users who want to get the Preview from the Store first need to go over to the official Windows 8.1 Preview download page and deploy a separate update.
Once you complete this step, a notification should be displayed on your screen, telling that Windows 8.1 Preview is available for download.
From now on, it’s all just a matter of time. Simply clicking install will start the updating process, as the Preview will be downloaded and deployed on your computer just like a regular Metro app.
Of course, the computer is then restarted and you’re provided with the standard License Agreement and the start-up tutorials to help you set up the new operating system.