My friend, purchase a $4 MetroCard from the Hudson Newsstand at the airport and follow these directions.

Step 1: take Q33 from the Main Terminal, or the Q47 from the Marine Air Terminal to the Roosevelt Avenue-74th Street Subway Station.

Step 2: at the Roosevelt Avenue-74th Street Subway Station, go downstairs and transfer to the "E" express train (Blue Line on the subway map). Take the Manhattan-bound train from Roosevelt Avenue-Jackson Heights to 42nd Street-Port Authority Bus Terminal.

Step 3: at 42nd Street-Port Authority Bus Terminal, exit the subway into the bus terminal take the Rockland Coaches bus route 9 from the PABT to Tenafly. The bus departs from gate 220 at the bus terminal and terminal at Clinton Avenue and US Route 9W in Tenafly. The fare on the bus is $5.55.

I hope this information is very helpful.

Good luck
Native New Yorker