With Customer Groups, you can create different groups and include all the customers entitled to receive a particular discount applied automatically to their sales.
To create a new Customer Group, go to the "New" button.
Add a name and select the discount and/or rate to be applied.
Note: Discounts and Rates must have been previously created.
Once the group is created, add the chosen customers to it, by clicking on Group Customers. Select the customer and click "Add".