The application has a few default websites in its list, you may add a new address that you wish to monitor by pressing the "Add URL" button. 

From the "Options" menu you can add or remove a web site and also to configure the alarm's settings. 

Click the "View Results" button in order to get an overview over the results, see the errors that the site may have and the maximum bytes. You can also see the last test report for a certain HTML address. 

You can customize the alarm settings in order to be alarmed at any error or only when the server is down, but before clicking "Ok" you will need to provide your e-mail address.