are you trying to leave a review? If so, you just find where the product is already listed under the vendor who offers it. Bring up the product description and then at the bottom right right, just below the full product profile from the vendor, click the Submit Review button. Then fill out the form and submit it.
If there isn't a product profile for that kava from that vendor, one would have to be made. And if there isn't a category for the vendor of the kava you wish to review, check the other vendors folder and they might be in there.