Extract the downloaded library to a folder on your computer. You may need to use a file archiver like WinRAR or 7-Zip to extract the files.
Download the cracked library you want to add to Kontakt 7. Make sure it's compatible with Kontakt 7.
If you haven't already, download and install Kontakt 7 from the official Native Instruments website.
That being said, here's the guide: