To activate windows 10 for free with cmd prompt follow the below directions.
After you enter into Windows 10 Command Prompt, you can copy and paste this command line: slmgr.
Next you can copy and paste this command line and hit Enter to install the Windows 10 product key: slmgr /ipk NPPR9-FWDCX-D2C8J-H872K-2YT43.
Another windows 10 activation key for free is TX9XD-98N7V-6WMQ6-BX7FG-H8Q99 for windows 10 home