Richard,
Welcome to VATUSA! You will actually need to join ZBW first before you can begin training there. To do this please click on "My VATUSA", then "Transfer Request" and click on Boston.
You will receive some information (some automated, some may be sent by a person) detailing how to go about requesting training.
Should you not hear anything in due time please reach out to Jamsheed Lovelace (zbw-ta@vatusa.net) and/or Clif Whitten (zbw-atm@vatusa.net).
Best of luck on your journey.