A family of Microsoft word processing software products for creating web, email, and print documents.
Which version of Office do you have? Did you install it on your new computer?
It is possible that you are being asked to activate a preinstalled trial version. I would suggest that you uninstall the trial and then install your own version.
As other contributors have said, after you installed, activation is usually straightforward (it will depend on which version of Office you have, though).