Native Instruments Kontakt loads sounds in two different ways and this depends on the product that you have purchased.
Requires the full version of Kontakt.
Kontakt files will load in the Free Kontakt Player but only in demo mode.
Can be used in either the Free Kontakt Player or the full version of Kontakt.
Once you've successfully downloaded the Kontakt Library, you can open the Free Kontakt Player in either standalone or plugin mode, navigate to the 'library' tab and then choose 'Add To Library'.
A window will pop up and ask you to select a folder that contains a Kontakt Player compatible library. Navigate to your installation directory and click 'Add'.
You should now get an option to Activate the library via the Service Center. Clicking the Activate button will open the Service Center inside Kontakt, and allow you to paste in your serial number and activate the product.
Please checkout our blog on the link below, which details everything you need to know about Kontakt.