All you need to do is send the blank
email this generates (with the word "Join" in the title)
and then respond to the confirmation email that you will receive.
You will then be signed up to the email list. Please note that there
will be no SPAM or other adverts sent to the list beyond genuine
branch announcements. Any replies sent to this list will only go to
the moderators and not to everyone that has signed up, so your
mailbox will not become full of questions about which pub people
will be in at a particular time!