Add a rating or review:

• Open Google Maps and make sure you’re signed in.
• Search for a place.
• Below the search box, click Write a review.
• In the window that appears, click the stars to score the place. If you want, you can also write a review.

Source: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwiv37vLw8zOAhXG8CYKHbH-D80QFggeMAE&url=https%3A%2F%2Fsupport.google.com%2Fmaps%2Fanswer%2F6230175%3Fco%3DGENIE.Platform%253DDesktop%26hl%3Den&usg=AFQjCNFFwXYJkp3eIopqbTJ1KfnZPFgiVg&sig2=mA9dvKwM0ZGSHVEOg0dSYA