I have an old Dell laptop which I use for streaming audio only.
There is Windows 7 Home Basic already loaded onto the laptop, and the person who had the laptop previously did not load a genuine Windows 7 Home Basic software. So I am seeing "this copy of Windows is not genuine" showing up all the time.

Now I have a genuine product key or activation key for this Windows 7 Home Basic, but I am at a lost.
How or where do I put in this product key so this message could stop coming up? I went to Control Panel, System, and there is nothing there that says "change product or activation key"

Help