You really need to research (Google Map) the distance between New York and Boston. It is very far. There is no bus service from the airport that I know of. If you insist on spending all your time travelling - you can take the Airtrain from JFK, transfer to the E subway train and get off at Penn Station in Manhattan. From Penn Station you can take an AMTRACK train to Boston. Otherwise, just fly there and be there in an hour and a half! (The same time it will take you to get on the train in Manhattan).
Bus to Boston