Connect computer to router with LAN.
Find out your router address:
Copy the address and put in web browser.
You will be asked for login username and password for router settings.
Put it in if you know it. If you don't know it or you haven't set it up. Search online for the default username and password.
Once you are in the router settings, go to wifi security and change the password.
If you have a router settings password but you forgot about it and cannot access router settings. Press and hold the reset button to reset and use the default login username and password.