Updating a second PC

Having now got the GWX icon, and found that the Sony laptop is compatable (see --> http://ift.tt/1LFLPXY)

I have the ISO dvd for updating the PC (and presumably can use the same DVD for multiple PCs)

However, I am confused about what I need to do next:

1. Do I need to create a totally separate email address for the Sony Laptop so I can associate Windows 10 to a different email account.
(Presumably I can create a new @outlook.com account? for this)

How do I go about this please

secondly - The Sony came from a shop, so it was all preinstalled, and I have no discs whatsoever.
From Disc Management on the Lappy, I have the following:

Should I update from scratch (keeping no files or programs), or just update as it is.
I have worries about drivers etc, but want to get as clean a PC as possible. There is nothing I desperately need to keep that I can't reload on, but I would like to create a separate Partition for Virtual machine stuff

Could I uninstall programs I don't want to keep, and then update?

What's best to do?

Thanks

Updating a second PC