Mailman wont deliver

I am trying to set up a mailing list to send out messages to many persons (approximately 3000) but I have no clue how to actually get it working. Im running mailman which comes with my server but so far, the most i’ve been able to do is to actually import the contacts email addresses, I cant actually send anything instantly which is what i really want to learn how to do.

Heeeelp. I really need it.