Sign In to MS Office Account
Go to office.com/setup and enter your MS office account credentials
If you want to reinstall office or repair it, you can re-verify your product key on setup page and can download older version of office
Office Setup page provide direct link for Microsoft support page where you will get Setting how to Open Get Help app in your computer system itself. Click on Contact support
Enter 25 character product key to activate office setup
choose country and language 32 bit or 64 bit and click next. Your key will be validated successfully.