How to change password
How to change password on my router
You need to sign in to the router, then change the Password.
See -> Recommended settings for Wi-Fi routers and access points
Recommended settings for Wi-Fi routers and access points - Apple Support
The Wi-Fi network name, or SSID (service set identifier), is the name your network.
And every Wi-Fi network name has a Password.
So sign in in the router and check and change.