For the convenience of finding addresses, open the contact pane. To do this, select the Menu Bar menu item View > Contact Pane. Or click F9.
Select the address book from the drop-down menu Address Book. To create a new contact or mailing list, click (additional menu) and select New Contact or New List.
Select a contact from the list, then click To, Copy or Bcc in order to use the contact in the email.