To earn this achievement you need to press the bottom right icon in the corner of the screen and when the achievement list pops up you will see the "show the love" achievement. Next to it is a little arrow. Press this button and it will take you to the rate this game screen.
Might seem obvious for some people but for me, i was waiting for it to pop up and ask me to rafe the game but it never did so i went looking to an option.
Hope this helps some of you out.