The same way as eclipse debugger. We haven't added smth special for debugging. You can search it in google. http://www.google.com/search?hl=en&ei=SDLIS6bdFIP8OZmOuaoF&sa=X&oi=spell&resnum=0&ct=result&cd=1&ved=0CAUQBSgA&q=eclipse+debugging&spell=1
Thanks for the reply.
What I did not figured out, was what is needed to get into a debugging state that will actualy stop at breakpoints for example. I tried it before and it didn't work for me. I tried it again usgin Debug as -> Debug on server, from my index page and it worked fine. I probably did something wrong before and did not realize it.