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.