Open the web browser that you use and type in the IP address for your router,and press the Enter key. http://www.routeripaddress.com/
< Router ip addresses can be found here
A window will open and then type in your routers default username and password,and press the Enter key again http://www.routerpasswords.com/
< Router usernames and passwords found here
Navigate to the Wireless Security\Network Security Settings Tab and open it to locate or change your Security Passphrase.
Use WPA or WPA2 because it provides better security.
Write this Security Passphrase down and put it in a safe place .
Save settings and close your browser.