Get off the RailRoad, look for the signs to the 8th Avenue subway line (A, C, E trains) and take the E in the UPTOWN direction for four stops.

While waiting for the E train, walk forward along the platform to the north end where the front cars will arrive.

Thus when you exit the E train four stops later, at Fifth Avenue (and 53rd Street), you will be coming out onto the street near Madison Avenue. Walk one block eastwards, to Park Avenue. Enjoy the walk!