They claim they supply the method or instructions. Here it's been real simple. Every W10 License at the shop, office and home is either pre-activated (many many laptops) or when we did need W10 the product key was in the packaging.
https://support.microsoft.com/en-us/help/12440/windows-10-activate notes where to enter this product 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.
Please help me as i dont know how to activate ?

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