The complications of farecard systems make it difficult to explain to another person how to work them. In your question, there is a piece of luck. The other day at Newark, I observed the crowds coming upstairs and trying to get onto PATH. My suggestion: Follow the signs to PATH. On the platform, near the turnstiles there are two or three machines selling Metrocards and Quickcards (on the same machine). Purchase a Metrocard for a value of $10 or so. Use an old $10 bill or two $5 or a credit card or a debit card. You will receive a Metrocard with a riding value of $12.
Note how it is inserted into a new turnstile with the illuminated green tower. (Avoid the two cash turnstiles at Newark. These old machines were balky the other day.) There is a slot in front of the turnstile and an picture of how to face the Metrocard into the slot. The machine grabs your Metrocard and instantly gives it back to you through a slot in the top, a few inches ahead of where you inserted it. The green tower will say something like "Enter" or "Go" and say "Value remaining $10.50" because it has deducted the $1.50 Path fare. Go through the turnstile. If another person is traveling with you, after you get through the turnstile, you may turn around and give the Metrocard to the other person to use in a similar fashion. It will be returned through the same slot.
On 32nd Street, between 6th and 7th Avenues, you will find M4 buses ready to start their slow trip north to the Cloisters or Fort Tryon Park. Pay your fare by inserting the Metrocard into the fare box as demonstrated by the sign. (There are small arrows on the Metrocard). The fare box will take your card, waste some seconds reading it, and return it to you. As a bonus, a free transfer will be encoded onto the stripe, good on any MTA local bus (except M4 and maybe some other routes) or subway station within the next two hours, 18 minutes. Your card will now have a value of $8.50. If a second person is with you, that person may also dip the same Metrocard to pay the $2 bus fare. The catch is that if two people later transfer together (within the two hour margin), a single swipe uses the two encoded transfers.
The same Metrocard will work on the trip home. These Pay-per-ride Metrocards are great because they work on PATH, MTA transit, and JFK Airtrain. The "unlimited ride" Metrocards work only on MTA transit. And my senior Metrocard ($1 ride) does not work on PATH, so I keep a spare pay-per-ride for my trips on PATH.
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If $10 is too high for you, you can buy Metrocards encoded for a lesser value, but you will not get the $2 extra value. The remaining value on your Metrocard from that excursion to the city can be given to a friend going to the city. If you pass the expiration date on the card, at a subway booth (not PATH) you can transfer the value of the expired card and get a new card.
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Please, if any reader FINDS AN ERROR in my narrative, correct it! All best wishes.