In order to use .jar files in NetBeans, you can either add the jar file to your global libraries or your local libraries. It sounds like you tried doing it locally without much success. I recommend adding a library such that you can just pick from your list of libraries without needing to reload it. I use NetBeans 8.1 so it may be just a bit different for 6.8.
What you need to do is go to Tools->Library
Then you need to click on New Library at the bottom left of the dialogue box.
AddLibrary
Name it and hit 'Ok'. Then, you'll add a new jar file by specifying your jar path. Hit 'Ok' again to save everything.
In order to use your new library, you'll need to then click on your Libraries folder in your project and add a new library. Select from the list of libraries the library you just created.
SelectLibrary
Finally, you import your individual files in your library using the #import keyword as per usual. If you want to import everything, you'd type something akin to
import MyNewLibrary.*;
To load a library the way you tried to do it, you'd right click the libraries folder and click "Add JAR/folder" instead of "Add Library". Then you'd import everything.
If you still for some reason cannot get your library to work, then you probably aren't importing using the right name. Or, you might be trying to load a static library without using the static keyword.