At times you'll need to add a customer to your project in order to communicate with them. Project Agents and Administrators can add Customers into projects.
From the project, locate the Customers link on the left-nav bar of your project.
The Customers screen will display showing all current customers. In the upper right hand corner you'll find a "Add Customers".
Correctly enter the email address and click the OK button. Do not try to add an organization. Now you can add that new customer to any existing ticket.