windows 10 key

I recently brought a windows 10 professional key from arcadefuture.com .But i dont know how to activate my windows 10 via that key.This is the link from where i got the key. https://www.arcadefuture.com/Microsoft-Windows-10-Pro-Professional-OEM Please help me as i dont know how to activate

I'm sure you guys get this question a lot so bear with me: I'm upgrading my Gigabyte H100M-S2H to a Aorus B450 M and I'm upgrading my i5 6400 to a R5 2600. What do I need to do before performing the hardware swap? I mean, driver-wise, also how can I do a fresh install of Windows with an OEM...