1. Launch a CMD as an Administrator
2. Type: slmgr.vbs /ipk xxxxx-xxxxx-xxxxx-xxxxx-xxxxx
3. Press Enter

This process might take several days (!!!) to complete. Wait for it.

slmgr.vbs command help

Referenced Instructions

Alternate Activation Gui Method

1. click START (gets you to the tiles)
2. type RUN
3. type slui 3 and press ENTER
   1. SLUI 1 brings up the activation status window
   2. SLUI 2 brings up the activation window
   3. SLUI 3 brings up the CHANGE PRODUCT KEY window
   4. SLUI 4 brings up the CALL MICROSOFT & MANUALLY ACTIVATE window
4. Type in your product key
5. Have a nice day.