Right when you finish the test, it will tell you the score, but that's all. Go back to the page where you started the test (the main CAT page). There will be a new line there, listing the test, and a link to "Review Results." That will show you the problem lists and a bunch of data.
From that same main CAT page, you can also click "Generate Assessment Reports." That will take you to a page where you can choose the test you just did and click "Generate" - then start to read through the reports.
Also, this article might be helpful as you look through the data:
http://www.beatthegmat.com/a/2009/09/23/evaluating-your-practice-tests