This is the main window of 1st Mass Mailer where you can see the tree view of your Mail Project that contains the Recipient Groups, Messages, Schedule and Sending folders 

In the Options window you may customize the SMTP and POP3 settings as well as the Recipient Fields, File Types, Domains and Preferences 

Here you can see the Add Schedule Item that allows you to select a time interval in which the messages should be sent and also the number of messages that you want to send and the pause between them 

The Add Message window lets you select the message's type, Subject, Body and Charset. You may also add attachments to the mail