BELOW WE MAY GET STEP-BY-STEP SCREENSHOTS,

Step 1 - Click on "Start" button.

Step 2 - Click on "Settings" button.

Step 3 - Click on "Update & security" button.

Step 4 - Click on "Activation" button.

Step 5 - Verify "Windows is not activated".

Step 6 - Click on "Change product key".

Step 7 - Type valid product key "NXXXX-9XXXX-RXXXH-XXXXW-XXXXV".

Step 8 - Click on "Next" button.

Step 9 - Click on "Activate" button.

Step 10 - Wait for some time

Step 11 - Click on "Close" button.

Step 12 - Verify "Windows is activated".

Step 13 - Again, verify "Windows is activated".