I'm sitting here using my Lenovo Yoga 2 Pro, which runs Windows 8.1, and have just noticed a little Windows logo in my taskbar. Microsoft is now offering free upgrades to users, where you can "reserve" your copy of Windows 10.
Once Microsoft makes Windows 10 available, you can download the new operating system, and download it to your device. You can either install it right there and then, or schedule a time that is better for you. Microsoft says that Windows 10 will require 3GB of download, and of course, your Internet connection.