I'm not clear on whether you've seen the piece, but that's the first step...
A review needs to be from your heart - what you saw and how you can put that down on paper. It's not always easy; sometimes you have to start writing, even if it doesn't all make sense and the ideas will come once you have the words on paper.
One way to start by going to the Alvin Ailey website (www.alvinailey.org
) - there is information there on the ballets, images and even a short video clip from "Revelations". Sometimes seeing images or video from performances can help spark your memory and your writing.