you would create a new customer in a similar manner as to create a new supplier: click on Search and select Supplier and Customer. When the Search Suppliers and Customers screen displays, at the bottom left is a Create New button. When you click this, you can select Supplier or Customer. Also note on the Organization Profile screen, there are 2 radio buttons, one for Supplier Yes/No and one for Customer Yes/No. These can be changed at any time.
Marking this as "Answered" but please keep the thread going if further questions, feedback or clarification is needed.