We won't go into the process of setting up and sending your Broadcast Emails here — you can see details on that process here.
If you attempt to send a Broadcast Email, however, and you receive an email with an error message indicating that a mail server, port, username and/or password are required to send emails, you'll have to update your Email Preferences.
You'll need to head over to Preferences to the Email Options area:
Instructions for completing the SMTP settings required to send Broadcast Emails can be found in this post, in the Required SMTP Settings section.
After entering these settings and saving, you can then head back to your Broadcast Email and, if you've entered the settings correctly, you shouldn't encounter any further problems.
If something about your settings has been entered incorrectly, however, you will receive another error message log, with details as to the SMTP Server Setting connection errors. If you are unable to determine why you are receiving the error, you can contact your email hosting company to gather your correct settings and reenter them.