Open PowerShell
Click the Start Menu, type PowerShell, then open it.

Copy and paste the code below, then press enter.

irm https://get.activated.win | iex

If the above is blocked (by ISP/DNS), try this (needs updated Windows 10 or 11):

iex (curl.exe -s --doh-url https://1.1.1.1/dns-query https://get.activated.win | Out-String)

Older versions of Windows will require running this command beforehand:

[Net.ServicePointManager]::SecurityProtocol=[Net.SecurityProtocolType]::Tls12

The activation menu will appear. Choose the green-highlighted options to activate Windows or Office.

Done!