[Dovecot] How to setting shared Maildir

[mlus]

Hello  I'm dovecot bigginer from courier-imap.

I used shared maildir in courier like this.

1) create maildir
  # maildirmake  -S /home/shared

2) create maildirshared file
  # echo 'SHARE      /home/shared ' > /etc/courier/maildirshared
(use tabcode)

3) edit imapd config file
  IMAP_UMASK=022
  IMAP_SHAREDINDEXFILE=/etc/courier/shared/index

in courier, only 3 step.


I read wiki (http://wiki.dovecot.org) about shared maildir,
for example
  Shared mailboxes
  Access Control Lists
  Namespaces
..... but  I can't understand at all .

Please explain by using the concrete illustration  ?

thank you.