From Penn Station, you can take the 2/3 to 42nd St (Times Square) and transfer to the shuttle or 7 train & take that to Grand Central.

If you're looking to get from EWR to W, the Court, you can also take a bus to Port Authority (42nd & 8th) and take the Shuttle crosstown to Grand Central. I believe that there are also some buses which go directly to the east side. Whether the bus is a good option or not depends on the time of day and traffic.