From the left menu, click on "Resources", then select the "Customers" link:
Click on "Create Customer" to add your first record.
In case you already have customers, you will be able to see all customers previously created, as below:
Use the action icons to edit/delete existing customers or the search box to quickly find customers on the list.
NOTE Customers already tied to existing accounts CAN NOT be deleted.
Click on the "Create Customer" button to create a new customer. The screen below will be displayed. Fill the fields accordingly:
Click on "Create" to save the changes.