A family of Microsoft word processing software products for creating web, email, and print documents.
Which Microsoft product do you have? If you have a subscription, you typically activate by signing in; see https://support.microsoft.com/en-us/microsoft-365-activation-licensing/office-install/activate-office-for-mac. This assumes that Office has been successfully installed on your Mac.
Which version of macOS do you have? After the mid July updates, you now need macOS 12 or later to run Microsoft Office. You also need a version of Office which licenses version 16.83 or later. See https://www.brandwares.com/bestpractices/2023/03/most-recent-office-you-can-run-best-practices/ and https://support.microsoft.com/en-us/office/lifecycle/officeinstall/update-m365-office-macos-ios .