Step 1: Ensure you've downloaded all of the Shreddage II RAR files. These are compressed archives that can be extracted using UnRarX on a Mac, or WinRAR on PC (both free). All files should be the same size (500mb) except for the final RAR, which should be smaller.
Step 2: Double-click on the Part1 RAR file to extract it. You only need to extract part 1!
Step 3: Move the newly-created Shreddage II folder to the desired location on your computer. This is where the library will reside. You should make sure that this folder contains subfolders like "Instruments and Samples". If there is another Shreddage II folder within it, move that folder instead.
Step 4: Open Kontakt 5 (or Kontakt 5 Player) either in your DAW, or in standalone mode. If you do not have either, download Kontakt Player from www.native-instruments.com. In the browser on the left, click the "Libraries" tab, then "Add Library" and select the Shreddage II folder you extracted earlier.
TIP #1: If you do not see a browser on the left-hand side, click the "Browse" folder icon at the top of Kontakt.
TIP #2: When you go to "Add Library", make sure you select the Shreddage II folder that contains Instruments,Samples, etc.!
Step 5: Close Kontakt and open Service Center, which should have installed automatically with Kontakt. You will be prompted to enter the serial number for Shreddage II; put in the code sent via email (also viewable on the same page as your Shreddage II download links).
Step 6: You're ready to use the library! You can access it anytime from the Libraries tab in Kontakt.