Before you can send newsletters you first go to components -> BwPostman. Klick to options in the upper right corner and configure BwPostman to your needs.
Then you have to create at least one mailinglist, where the subscribers will be stored.
Next I suggest to create some test-recipients, then you will be able to test the usage of BwPostman and the template of HTML-Mails.
For personalizen newsletters you can use follwoing codes:
lastname = [LASTNAME]
firstname = [FIRSTNAME]
first- and lastname = [FULLNAME]