reset Password for preferred wifi network on Mac OS version 11.6.4

Do you mean it has a new password and you need to connect your Mac to it using the new password? Or do you mean you want to change the current password it has to something different?

For the first one, go to System Preferences->Network->Wi-Fi->Advanced, Select the Wi-Fi tab if its not selected in Advanced, then find the Wireless network in the list, and then click the minus [ - ] button to remove the network. Once removed, click on the Wi-Fi icon on the menu bar and connect normally again entering the new password for it.

For the second one, you will need to access your Router's configuration webpage as outlined in your router's documentation and change the WiFi password there to a new one. Then follow the steps for the first option to update the password your computer uses.