This will paste a copy of the letter into notepad so that you can add your name to the list. If you want to do your postings in different sittings, you'll always have this file to go back to. Fill in the Subject, this will be the header that everyone sees as they scroll through the list of postings in a particular group, click the post message button. You may eventually want to rent a P.O.Box due to the large amount of mail you will receive. If you wish to stay anonymous, you can invent a name to use, as long as the postman will deliver it.
Some work is involved.