You can add clients two different ways.  

1 - You are welcome to go to the Clients area, and click ADD CLIENT. You will then see the overlay where you can enter the client's basic information. (But not the individual contact information – that will come later).

2- You can also add a new client when making a new project. Simply go to projects, and click ADD PROJECT. In the overlay, you will see the field for CLIENT NAME. Just start typing the client's name, and any known client will appear, which you can then select. If no match is found, you will then be able to type the name of a new client. 

This new client will then be added to your database for future use and editing.