you won't find it on your computer, it'll be on your router.
look on the router and you should be able to find a login/password or perhaps a security key listed on a sticker somewhere then do the following.
plug your PC directly into one of the router's ports
open a web browser
type 192.168.1.1 in the address bar
enter said login/password
change settings as you feel fit after logged in
the end