Reviews are pretty simple (once you get the first one under your belt). If you look in the state forums, you'll see several that are available to post reviews in. The Independent provider review forum is for girls that work for themselves, the Agency reviews are for those who you know work for an agency. Similary, there's a forum for reviews of AMP or Strip Club girls. You basically just navigate to the correct forum and press the New Review button, which will give you a form to fill out and then Submit the review. As a first-time reviewer, I'd recommend you look at one of the review tips threads, if you want to do a good job (there's a link in my signature block to a popular one).
If you take a lot of time writing like I do, it would be a good idea to create it in advance on whatever word processing program you prefer, so that you have all the info at your fingertips. That will save time looking all over the place for info when you are in the review form and prevent a possible time-out issue, which would require starting over again.