Activating Microsoft 365 Apps for Business with a product key
You might have a product key for Microsoft 365 Apps for Business. If so, there are two separate actions you might need to do with the product key.
Activate your Microsoft 365 Apps for Business subscription
If you purchased a Microsoft 365 subscription from a retail store, see Enter your product key for Microsoft 365 Apps for business.
If there's an error message when you try to redeem a product key, see Problems with your Microsoft 365 for business product key?
Activate Microsoft 365 Apps on your device
Use your Microsoft account, not your product key, to install and activate Microsoft 365 and individually purchased Microsoft 365 Apps, such as Project, Visio, Word, Excel, or Outlook. For more information, see Office is prompting me for a product key.