The text of the message usually requires only four words: SUBSCRIBE listname your first name your last name. The first message you receive from the list is the most important. It tells you how to distribute messages of your own and how to remove your name from the list. For example, to subscribe to the Windows for Workgroups list, John Doe would send a message the the text of "SUBSCRIBE WFW-L John Doe". Do not include the quotes in your message. That's all there is to it.
This method can vary slightly for some lists, so it is necessary to pay attention to the correct format for the list to which you want to subscribe. Some may require your e-mail address instead of your name. Thanks to Windows Mag 4/95 for this info.