How do I upgrade Win 10 to Win 10 pro with a product key?

[Windows Central Question]

how do i upgrade win 10 to win 10 pro with product key?

I've just purchased a new Lenovo yogo 900 with win 10 installed and also purchased a win 10 pro upgrade in store. how do I activate the win 10 pro as I don't know how to get win 10 to boot from the provided usb stick? thanks