1. Click the Wireless icon on the lower right, next to the clock.Now open Network and Sharing Center.
2. Click the Manage Wireless Networks link on the left column and click on the Wireless Network icon.
3. Choose Properties and go to Security tab.
4. Click the Show Characters check box to reveal the Network Security key
5. Write down the security key. Enter the security key on your iPod Touch.
I hope this can help you.