Login to it as the administrator in your Cpanel under Mailing lists by clicking on edit. There you can change all manner of settings for the list. You can find out more about a setting by clicking on the "Details for..." link under each option. You may add users in bulk there or they can visit your Maillist Info page at
http://yourdomain.com/mailman/listinfo/listname_yourdomain.com. The same goes for unsubscribing. There will also be a link there for the address to send messages to the list. You can use any email program to send to the list using that address.
The list can be set to either send out each message to the subscribers as they come in or to moderate messages which means you would have to approve every message to the list, or to send in digest form which compiles all the messages for a specific time period you set into one message that is sent out periodically.
If you want to create a one-way list where you email them only (they don't email the list), you can hide the mailing list address by editing the List Info page and the welcome that goes out to new subscribers in the Admin section.
Here's a link to the mailman FAQ:
http://www.python.org/cgi-bin/faqw-mm.py
