This was presumably clear from the achievement description, but just for the sake of really spelling it out:
Make sure you have the Tranquility theme set. Since these are wild tiles, you CAN match them with each other (i.e. match an N with an S), but make sure you do not do that. Make sure you have a seat of 2 of each tile exposed, then in order, match the two N tiles, the two E tiles, the two S tiles, and lastly the two W tiles. Don't make any other matches in between, and do not mix and match the tiles.