Steps
1)Go to your browser
2) Type IP address 192.168.0.1
3) User name(none)
Password (admin)
4) click wireless
5) primary Network
6) Change The password at the Pre- shared key
7) bottom part apply , the network will be disabled and go back to your settings . Enter your new password
Note: if you hard reset your modem the wifi name and password will be back to original default settings.