Follow these steps and get the Norton setup key.

In the beginning, enter into the Norton account by hitting the sign-in tab followed by entering all the asking details at “www.norton.com/setup.”
Once you have successfully entered into the Norton account, hit the Devices section.
Search the device for which you wish to retrieve the product key.
Then, you have to note down your product key from the system’s screen.

Read more - norton.com/setup