Proper method to change WiFi log/password?

I had spent a day setting up a new RPi/LibreElec for a co-worker and it worked perfectly on my Wifi network with my user login/password.

Upon taking it to his house, I was unable to find how to change to his network eventhough the system did display the new network [and a few others in the area].

Everytime I tried to select that new network, even tried "c" for context menu, it would immediately try to connect without prompting me for new credentials and of course it would fail.

Out of desparation I just reset to default and of course lost my previous day's setup, addons, etc.

Now when I selected the new network it asked for the code [cable modem/router which only used a code not login/password] and it tried to connect but said it failed when in actuality it succeeded. I think the Rpi was faster than the router acknowledeging hence the bogus failed message.

As I may go back and utilize a hardwire ethernet vs WiFi, I hope there is a less disruptive method to change the network settings.

I know I must have done this wrong so a new method would be appreciated to change and existing network connection.

Thanks,

Seriously, nobody has ever needed to change the WiFi network log on credentials?

I cannot believe what I did, while it worked, is the proper method as all my other configurations/addons were gone.