Yes.
Same account you use for everything.
Skype, windows, etc.

You do not need a key to install.
Log in with your microsoft account after your done and windows will be activated.
Did this myself a few hours ago.
Good luck. :)

I have just now installed Win 10 clean install.
Pro version if it matters.
And apart from some hicups that i got sorted everything went smooth.
When it comes to the windows 10 instalation key. You...

I have the same issue.
It is really annoying. And it affects everything. Even games.