Joining a mailing list is very simple. You send an e-mail message containing a 'subscribe' or a 'join' command to the administrative address of the list. Usually, you will then receive a message informing you that you are now subscribed to the list. It is important to remember that the 'subscribe' message, and other administrative messages as well, should go to the administrative address, not to the list itself. If you send such messages to the list itself, they will normally be distributed to every subscriber to the list, which besides generating a certain amount of irritation, wastes everyone's time including your own, as it your message won't have achieved the intended objective.
Some lists are very active and generate a lot of messages each day.
With others weeks may go by without any traffic. If you belong to a mailing list you need to learn to cope with the mail it generates. The initial filtering of messages can be done by scanning the Subject field of messages and deleting those you recognise as not relevant to you. Whichever filtering process you use, you'll need to act decisively on the messages which remain. Decide which messages should be discarded, which acted upon, and which retained for reference, then follow up accordingly.