The "Daily Bonus" is a great way to gain extra coins for free!
After passing level #5 you can start collecting the daily reward!
Once you collect it, a timer is available when you enter the game, indicating the remaining time until the next reward is available and so forth.
(Tip: The Grand Prize on day #7 contains an awesome surprise!).
Make sure you enter the game on a daily basis to collect your daily reward and also ensure you have push notifications turned on for the game, so we can remind you when the reward is available.