SMTP Settings can be set from Administration > System settings > Main > SMTP settings.
You can test the configured SMTP settings using the button with the letter icon, which is located on the header row of that settings table.
It opens a pop-up window where to you can insert an email address. After you press 'Send' button, test email is sent to given address using the defined SMTP settings. If test email is delivered successfully, SMTP settings are working correctly.