This YouTube Video explains how to add a .JAR file to Netbeans.
Here are the steps outlined in the video:
Download the needed .JAR file from the class website at uzza.us. Right-click on the JAR file to download it. Single-click on the .JAR file and copy it (CTRL-C in Windows).
When creating your NetBeans project, in the "New Java Application" or "New Java Project with Existing Sources" window, click the box labeled "Use Dedicated Folder for Storing Libraries".
Go to your hard drive and find "NetBeans Projects". Go into your project and into the "lib" folder. Then go into the "CopyLibs" folder. Paste the needed .JAR file into the "CopyLibs" folder (CTRL-V in Windows).
Go to the Projects window in NetBeans. Look for "Libraries" in your project and right-click on Libraries. Choose "Add JAR/Folder". Browse to the .JAR file and click Open to add it to Libraries.