Navigation : 

Go to : Money Manager >> Accounting Settings >> Discounts and Coupons.

Under this page, you will have the options to create discounts and Coupons for your clinic.

A> Add Discounts/Coupons : 

Note: If Default is checked, the Discount/coupons for which it is checked will be the default discount applied when you are trying to provide a discount for the client.

Please add all the details in order to create a Discount/Coupons and click on Save.