How can I send a message to all in my address book

You need to create a mailing list. As the name implies, this is a list of email addresses which are taken from the address book. (The address book often contains other information, e.g. a person's physical address, the company they work for etc.). Then you send the message 'to the mailing list' and a copy of it goes to each address in the list. Instructions are here: https://support.mozilla.org/en-US/kb/how-create-and-use-mailing-lists-thunderbird