The second way is a lot more simple however may not be supported by yahoo indefinately. Simply send a blank email to BritishKillifishAssociationemail@example.com, and follow the instructions in the reply
This mailing list is open to anybody
interested in killifish, but is aimed primarily at UK keepers.
Discussion may be geared specifically towards the BKA, or simply on
killikeeping in general. You can read all old messages on the associated webpage, which also contains file upload space, shared bookmarks, and chat area