How Does Princeton Review's LiveGrader Work?

Okay, so I bought 2 of Princeton Review’s (TPR’s) SAT books, (Cracking the SAT and the practice test books). In both of the books TPR says I should make use of their LiveGrader service and get my essay (the ones I solved on the practice tests) marked. I went on to see on how to use this LiveGrader service and literally everything I could find on TPR’s website was: http://www.princetonreview.com/college/sat-essay-livegrader
The link doesn’t tell us anything about how to use the LiveGrader. I called TPR at 4 am (since I live in Pakistan) and the call didn’t prove fruitful at all as the guy behing the phone had no idea what I was talking about. Can anyone help me on this, I have a few essays, typed up, that I want to get marked by the LiveGrader.
Also, other than Princeton Review, would you suggest that use some other books? (A few people suggested Barron’s and Collegeboard but I don’t think they’re necessarily better, as no one has been able to provide a valid reason why)