If it's on your computer it may be under Wireless Networking -- but the password will probably be invisible or asterisked.
So see the literature which came with your router for how to access the user setup screens in the router. Once in go to wireless security and review or renew the wireless security type and password. WPA PSK TKIP is the most common security type in use. Make a note of the SSID.
Go to wireless mode and ensure that it's set to a protocol matching both your computer's wireless adapter and the ipod's wireless (mixed mode is a safe bet).
Disconnect ethernet cable.
Go to the computer's wireless networking setup screen and see if you can detect the router's SSID (wireless call sign). Select that network and make sure you can still connect to the internet.
Apply the wireless security type and password to the ipod's wireless networking setup screen.