Well, the easiest way would be an existing FPGA development board with etherNet support.
Something like this is pretty inexpensive way to get started. About US$100 at most suppliers.
https://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=253&No=1140&PartNo=2#contents
It is not a CycloneII EP2C5 which is at this point old, almost obsolete, technology. But a more recent Cyclone10 LP series part.
If you are specifically looking for EP2C5 (or any CycloneII series part) you are going to be disappointed.
The EP2C5 is a pretty low end part and not common in development boards.