On the lower level of Port Authority Bus Terminal there is an information desk all you need to know is what gate the bus is departing from then get in line then the bus driver will ask you for your ticket.
Head downstairs of the Port Authority Bus Terminal, all the arrival/departures of buses are located there and also an information desk you can use for inquiry of all gates for departure.
As you pass the information booth, you make a right to the stairwell going downstairs under "Gates 60-85" and you should see the Greyhound sign.
You have to go down to the lower deck and if you can't find your way just ask the guys in the yellow vest and they'll be able to direct you to the correct gate
It's gate 80 second floor from the street level you can check in right on the bus.
Lower level
You also can ask anyone wearing a yellow vest over their shirt at the Port Authority Lower Level. You can use the elevators and escalators to get down to where the busses leave from. The ticket counter is the floor above where you go. Hope this helps you also.
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