Download Office 2021 Below: 

Go to https://setup.office.com/?ms.officeurl=setup and sign in or create account. Important Note. These are not the details you used to sign up here!  

From the Office home page select Install Office.

(How to activate Office)

•        If you have uninstalled another version, please Reboot first.

•        After installation open the app.

•        Enter your product key.

•        Click "I want to activate the software over the internet".