From the main menu click on Units and choose All Units.  

Choose the “Apply Unit Based Discount” radio button, it will list section that displays available discount types below on it.

By using the check-boxes you can choose the discount then the unit you wish to avail

Simply hit on the Apply button to avail the discount over the selected units.

We can view Applied additional services from all units and click on delete button if you want to delete any service added