Customers are split into Ledger and Sales Ordering customers and therefore the customer addition and maintenance is accessed in two ways.
From the Sales Ledger UAM customer selection via the 
icon. For full sales and ledger customer addition and maintenance as well as prospect customer conversion. And from the same maintenance icon from the Sales UAM customer selection for prospect customer, sales customer and delivery customer addition.
To maintain the flow of the help option be select Customer Maintenance, held within the Sales and CRM section.
For Customer Selection please select