A family of Microsoft word processing software products for creating web, email, and print documents.
How did you purchase your Office product? For example, if you purchased online via a third-party seller, you often get the product key in an e-mail. Contact the seller if you haven't been able to access the key.
On the other hand, if you purchased directly from Microsoft, most likely your product is already associated with your Microsoft account. Go to https://account.microsoft.com/services and click the Install button.