When they have earned enough points, you can start redeeming rewards. The rewards you have created will appear in the Ways to Redeem section of the widget : 

 

When a you clicks Redeem on a reward, a discount code will be generated that they can copy and apply to their next order at checkout. Each reward is worth a certain amount of points. Once a reward has been redeemed, its points value will be deducted from the your total.

If a you redeems a reward and wants to use it later, it will be saved in the Rewards section of the app widget.