How can I get from Newark to JFK?

You can go by train or buses, but you will be better off if you take the special buses You won't have to walk

Public transportation between EWR and JFK is abysmal and not recommended for anyone but the young, hearty, adventurous, and especially LOCAL. If that sounds like you, go for it and be prepared to walk and ride trams, trains, busses, and subways. Otherwise if you Google it, there are some private bus companies that do it. Take your pick. No matter what, give yourself A LOT of time. As much as 2 hours, and that's without any unexpected hassles. Hope you're not trying to catch a plane on a tight connection.

You may go by bus. Please check in Google for details.