If you are asking what I think you are asking, then these cannot be used stand-alone. This is a shield and needs to be plugged into a host board such as a Uno or a Mega 2560. The shield communicates with the host board via the ICSP bus and one additional (CS) pin (usually pin 10). Since the ICSP bus is presented also on pins 11 - 13 and pin 10 is used for CS, when the shield is plugged in, pins 10 - 13 are reserved for Ethernet and you cannot simultaneously use them for anything else, but you can use all of the other pins as you would normally.
As for how you use the Ethernet shield in your sketch, here is a reference to the Arduino Ethernet library with some examples:
The examples can also be found in the IDE under File -> Examples -> Ethernet.