How to send mass email

On the Mass Emailer tool, HOW DO YOU SEND THE EMAILS??  The only button is "Queue" then the emails go to the "Queue Status".  How do you SEND the emails?

You have to have an e-mail account set up on your server to send them from and then set up the cron jobs for it.

which command I can use to flush the mail queue?

thanks

Admin -- User -- now select all the members you want to send email... type the matter in bottom box and hit send.