To enter a password for the WiFi connection on a compatible Windows machine, click the network button on the task bar in the bottom right corner of the screen to open all available connections. Next select the correct network name, type in the password you've been provided with, and click "connect."
Wireless passwords on already-connected machines are in the "properties" tab of the network in question. With administrator permission, the text box displays the characters of the password. The password can then be copied and used on unconnected computers.
Without a password, a computer with wireless capability can still connect to a network if the network's router is accessible. Select the desired network and press the WiFi Protected Setup button on the network's router. The WPS button will then connect the computer without requesting a password.