You can use Berkeley-Visitor while on campus without any log in information, however, ultimately you should connect your devices to the private campus wifi. You can connect to Eduroam Wifi on campus using your username and password (formerly, the system was called AirBears but has since migrated). The tricky part is that you will need to find your wifi passcode, which is different from your usual login. 

Please follow the instructions from the UC Berkeley website

Note that eduroam might also work at other institiutions, which is pretty neat! Sometimes it does not work, so don't be shy to use Berkeley-Visitor sometimes! Find some other wifi options HERE.