Click on Start >> Run
Type 'CMD' and hit enter, you should see the black DOS prompt screen
type 'ipconfig' and hit enter
What you see against Default Gateway would be the ip address you need to go to setup your router (example: 192.168.1.1)
Hope that helps!!!
Open the web browser that you use: Firefox,Google Chrome or Internet Explorer and type in the IP address for your router,and press Enter.
A window will open and then type in your routers default username and password,and press Enter again
Username and Password can be located on the side or bottom of your router
Navigate to the Wireless Security\Network Security Settings Tab and open to locate or change your WEP or WPA Security Passphrase.
Use WPA because it provides better security.
Write this Security Passphrase down and put it in a safe place to access when needed.
Save settings and close your browser.