If you bought a new Office product key card, or you received a product key when you bought Office through an online store, go to https://setup.office.com/ and follow the on-screen prompts. Redeeming your product key is a one-time process that adds your new Office product to your Microsoft account. When you're done, you'll use your Microsoft account, not your product key, to install and activate Office.

your Microsoft Account:

Enter your Product key:

Install your Office: