Hi Mona,
I am not sure which OS you are using but we are trying to narrow down this scope and provide the best recommendation. Most of the DE2 documentation is captured as below link:
http://www.terasic.com.tw/cgi-bin/page/archive.pl?language=english&categoryno=165&no=529&partno=5 For existing Linux documentation that closes to DE board Wifi configuration was the DE1:
ftp://ftp.altera.com/up/pub/altera_material/16.0/tutorials/linux.pdf Those are the standard Linux configuration and you can refer to section 2.7.2 onward. Let us know if this helps.