First confirm your default gateway IP address (if you dont know it)
in windows earch type CMD and click on the Icon
Open the command prompt  and type in the word ipconfigure  as in the image below
Note the default gateway address,
  which isn't necessarily the same as the one in the image but could be something typically like
192.168.8.1 or 1.1 or 0.1 or .0.254 or 10.0.0.2  or any other variant .

Open a web browser, typically Google Chrome or mozilla Firefox or edge etc. 
In the address bar at the top type in the default gateway address  noted in the command prompt request,
typically there will be a password challenge
username should be admin if requested
Password will probably be zaq1!zse4$ or could be admin 
press enter
for Wi-Fi settings in circle 2 in the middle of the page
click on settings

 in the 2.4 GHz tab note the Current SSID network name
then the password would be encrypted to dots
click on the display password option to see the current password
Change the password to a new suitable password.
Click apply on the bottom right-hand side
Click on the 5 GHz tab and do the same.
Open any device that has access to the Wi-Fi network and test the new password settings.
Then close a web browser once you've confirmed that the settings have been accepted and are working

Click on the 5 GHz tab and do the same.

Open any device that has access to the Wi-Fi network and test the new password settings.
Then close a web browser once you've confirmed that the settings have been accepted and are working