The Arduino® Ethernet shield stacks on top of the Arduino using the shield interface, which you can find on the Arduino Uno, Arduino Mega, and the other variants of the Arduino hardware.
To connect the Arduino Ethernet shield to Arduino hardware and your PC:
Insert the Ethernet shield firmly on the Arduino hardware.
An Ethernet shield stacked on the Arduino hardware is shown in the following figure.
Connect the Ethernet shield to the network router, or to PC, using a RJ45 cable.