If you mean adding 3rd party libraries, such as bouncycastle or SerialIO, go to Project ... project properties (or default project properties if you want to add the library to every project). On the first page, you'll see a tab that says 'Required Libraries', click the tab and then click on 'Add'. A window will pop up with a list of already defined libraries. If your library is there, just click on it and add. If not, click on 'new' then another window pops up where you can add the class files (including jar files) for your new library (example: c:\bouncycastle\classes\bouncycastle.jar), add source files if needed, name your library, etc. I hope this helps.
My, my, aren't you a big fella. Here, have a tiny ad: