Take the Airtrain "jamaica station" route train at your terminal be careful, there other route trains. Its $5.00USD must buy a "pay per ride" metrocard. Then catch any Long Island Railroad train into Penn Station were you catch your other train on NJTransit train called the NorthEast Corridor(NEC) to Trenton. Go to NJTransit.com for schedule and fares. Good luck!
Take the Airtrain "jamaica