wireless networking - Providing passwords to multiple users on a wi-fi network

I have a wi-fi network that is being used by more than 400 users. Right now they are given access by a single password which the system administrator types on the individual workstations during the initial login. After that each time they try to connect to the wi-fi,they are automatically provided access. How can this be eliminated by giving each individual user a password that they already use for other applications in the say local network?