Changing a Wi-Fi password in a Linux GUI environment is simple. Open the network manager and update the password in the security tab of the Wi-Fi connection you wish to alter. However, if you have to use the terminal, things may get a little advanced. The easiest way to achieve this is to edit the file containing the Wi-Fi connection configuration details in the "/etc/NetworkManager/system-connections" directory. Open the file and change the psk value in the "Wi-Fi Security" option.