You can use the Google Fiber app to change your Wi-Fi password.
To change your Wi-Fi password:
- Touch Network
.
.- Touch Edit Network Settings.
Your Wi-Fi network information will be displayed.
- Touch the Primary network password field and enter a new password.
You can see your password by touching the visibility icon 
.
.- Touch Save; an alert asks you to confirm the changes.
- Touch Confirm to proceed with changing the password.
After a short time, your Wi-Fi password is changed.