Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Microsoft 365 is a subscription based version of Office, it is not free, you can subscribe to that either monthly or yearly.
https://www.microsoft.com/en-ie/microsoft-365/buy/compare-all-microsoft-365-products
If you need a free version of Office, the only versions that are free are the web based versions, but thye have limited functionality compared to the locally installed versions of the Office apps.
Word
https://www.microsoft.com/en-ie/microsoft-365/word
Excel
https://www.microsoft.com/en-ie/microsoft-365/excel
PowerPoint