You need to help us a bit more than this...
You just bought what ?
Let's assume it's a Fredo6 extension ??
Have you downloaded/installed 'it' ?
Have you downloaded/installed the latest LibFredo6, which it also needs ?
Have you installed the SketchUcation Tools which will work the licensing code ?
Have you restarted your computer to sync everything ?
Have you read and understood the guidance for buying and saving your license file[s] onto your computer ?
Have you tried to validate that license for the extension in it's submenu item under the Tools menu ?
There's a lot you haven't told us...
Please help us to help you...