Open http://www.ninemoons.com/mailman/listinfo/diveadx in a browser and you should get a window that says

"General DIVEADX mailing list" with some fields to fill in.  

Put your email address in, your name if you want that will be visible to other people, 

and pick a password to put into the two fields where it asks for a password.  You don't need to fill in
or change anything else.  Click on the "subscribe" button.

After some period of time (10 minutes or less?) you should get an email
from the automated mailing list software at ninemoons.com that looks
something like:

  Mailing list subscription confirmation notice for mailing list Diveadx

  We have received a request from 64.220.152.100 for subscription of
  your email address, i.e., "fnf@diveadx.com", to the diveadx@ninemoons.com
  mailing list.  To confirm that you want to be added to this mailing
  list, simply reply to this message, keeping the Subject: header
  intact.  Or visit this web page:

    http://www.ninemoons.com/mailman/confirm/diveadx/b809e793205ce1f16d999adc970f610708cba91b

When you get that email, click on the link that looks like the one
above with the long string of numbers at the end.  That will confirm
to the list manager software that you were the one that signed up your
email address.  After that you should get another email that starts of
something like the one I got:

  Welcome to the diveadx@ninemoons.com mailing list!

  To post to this list, send your email to:

    diveadx@ninemoons.com

  General information about the mailing list is at:

    http://www.ninemoons.com/mailman/listinfo/diveadx

  ...

You don't need to do anything with that but save it for future
reference.  Let me know if you have any problems.

Fred