If you don't have a Google profile, it's really easy to create one when you click on the link:
1) Click "Sign in" at the top right corner
2) Click "Create account" found just below the login box
3) Complete the fields on the next page, agree with the terms and press "next step"
4) Click "Continue"
5) Press the "Write a review' button! (if you can't see it, press the grey down arrow first)