Ok, I got it.
run from the command line.
javac -cp /directory_where_the_.jar_file_is/java-libpst.X.Y.jar Test.java (it should be in the example director and is available on github)
This outputs a file Test.class. The program takes a command line argument so put a .pst file in the same directory.
again from the command line
java -classpath /directory_where_the_.jar_file_is/java-libpst.X.Y.jar Test somePstFile.pst