Here is how to connect to the SPI bus kiranjose.com.
You will need to find a ENC28j60 Arduino library. The standard Arduino Ethernet shield uses a W5100 controller so the standard Arduino Ethernet library included with the IDE will not work.
Maybe this library can be made to work TrollMaker.com is for sale | HugeDomains.
This link also has a library http://www.geeetech.com/wiki/index.php/Arduino_ENC28J60_Ethernet_Module.