You have a separate password for each email list which is generated automatically when you become subscribed to the list. You do not need a password to send or receive email to the lists. You will need to obtain this password if you want to read the WWW list archive. Once you have the password you can change it via the WWW interface.
If you do do not know your password for a list or you have forgotten it you can get a reminder of the password via email or via the WWW interface. If you've forgotten your password and haven't saved the welcome message or any reminder messages, you can always get a reminder through the web interface: The summary of the email commands is here: here
If you do not receive the password reminder email after doing this, make sure that you typed your email address correctly and that the address you used is, indeed, actually subscribed to that list.
For security reasons, Mailman generates the same member options page regardless of whether the address entered is subscribed or not. This means that people cannot use this part of the web interface to find out if someone is subscribed to the list, but it also means that it's hard to tell if you just made a typo.
You can also get a reminder using the email interface,
Commands can appear in either the body or the subject of the message. (See here for more information about sending mail commands.)
If you are still having problems, do not give up in despair. I suggest you email one of the other members of the collaboration or <email@example.com>