If you are taking the subway, then take the AirTrain to reach subway station outside the airport (either Jamaica or Howard Beach). At these stations, you will be required to present your ticket at the gates. The ticket costs $5. You can also get combined AirTrain and Subway fares in one card for $7.75 ($2.75 extra for the subway ride). These stations are staffed, together with vending machines.
Ask information from any jfk personnel's how to get to Airtrain. $5 per person. Take airtrain to Subway. Ask at Subway booth for directions to your destination. Subway is $2.25. You can Google for details.
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