The NJ transit train is the easiest way but also to get to and from the Pru Center you may just want to take a cab as it might be quicker.

Here is the train website for NJ transit. Look under the Northeast Corridor line for trains from Newark Airport to Newark Penn Station (this is where the Pru Center is) and then it also goes into NY Penn station (at 34th Street)

http://www.njtransit.com/sf/sf_servl...ainSchedulesTo