How to do a fresh install of windows 10 with windows 7 key ?

[P.B]

Okay so all my pcs are valid for a windows 10 upgrade. my htpc and gaming pc currently have windows 7 with keys and eligible for an upgrade to the new software.

My question how can I do fresh a install do I just download a windows 10 disc...(if so which one ?)

and just put in my windows 7 key ??

Thanks for any help bit clueless here

 

[P.B]

But what happens if I upgrade my pc will I lose my copy

 

[P.B]

so re format windows and as soon as its done it will upgrade to windows 10 ?