Click on relationships on the left hand side of the screen.
Click on Manage Customers.
Click on "Add Customer" on the right hand side of the screen.
Select Business Consumer or Consumer from the drop-down box and type in the details of the customer. Then press "Submit".
If all of the fields were filled in correctly, congratulations you have successfully added a customer. If there is something wrong, an error message will appear and it will say if a field was filled out incorrectly and you might need to make a adjustment to it.