simple type cmd into the run command and then cd\
now type ipconfig
this will show you the ip adress of your default gateway
which is your router
or
open an internet explorer and type 192.168.1.1 on the address bar.
it will prompt for user name and password. if its linksys leave user name blank and give password as admin.
in the setup page go to wireless settings.
there you will find SSID.
also check wireless security if its enabled note the key.
now go to your computers and scan for SSID.
enter the network key if it prompts .
for further assistance you can approach at this source at
http://www.iyogi.co.uk