Hello, friend!
The procedure is as follows:
On the main menu, choose WLAN > 2.4G/5G Basic Network Settings.
On this page, you can change the Wi-Fi password.
You can also enter a new password and click Apply for the new password to take effect.

Note:
For some ONTs, you can configure a Wi-Fi password after choosing Advanced Configuration > WLAN > 2.4G/5G Basic Network Settings. In on the ONT web page.
Thanks!