The Send Email section is where you generate your Customer List based on the Product selected in the Show Product box. If you have specified a Type after generating a key, you can also search for Customers based on this information.
Once you have decided on the Customers you would like to send email to and selected them, choose a MailingList Email Template from the Use Email Template box. Then press the Send Email button.
Keys are sent by email based on the information provided in the General Settings section.