Write your review.
A few things Apple suggests you keep in mind:
Reviews are limited to 300 words.
Apple does not edit reviews, so triple check your spelling and grammar before submitting them.
Avoid the following things: Single-word reviews, Bad language, Contact information (email addresses, phone numbers, etc.), URLs, Time-sensitive material, Alternative ordering information, Comments about non-product related issues such as service and support, resellers, shipping, sales policies, other Apple partners or Apple topics not directly related to the product's features or functionality.