This is a two-step process if you are using IntelliJ 9 or higher.
Open the project structure and click on "libraries". Add the directory containing the JARs you are interested in.
Then click on "artifacts" and make sure your libraries are in the WEB-INF / lib of your deployment.
JAR-, Jetty, (, JAR- JAR ), Jetty/lib, . WEB -INF/Lib.