Question about using protege owl API to develop java app

I followed http://protege.stanford.edu/plugins/owl/api/guide.html this
website to try the "Hello World" java app. But when I was following the
"Getting Started" section, i got lost.

"add all the JAR files from the installation to your project classpath. Set
your compiler output path to plugins/classes." By following this statement,
i don't know why i still got import package problem like follows:

import edu.stanford.smi.protegex.owl.model.OWLModel;
import edu.stanford.smi.protegex.owl.model.OWLNamedClass;
import edu.stanford.smi.protegex.owl.ProtegeOWL;

When I compile the Hello World app, all the packages are not found.

I want to ask what i need to place in the directory so as to
successfully run the Hello World program provided in the "Getting
Started" section.