Anytime you join a password-protected Wi-Fi network on your Mac computer, you have the option to save the password and automatically connect to the network when in range. However, if the network administrator changes the password for the network you must also reset the Wi-Fi password on your Mac to the new password for the wireless network or your computer will not connect. Fortunately, changing the password for any secured wireless networks saved on your Mac is a simple and straight-forward task.
Click on "Apple" symbol on your Apple desktop, located in the upper left of the screen. A drop-down menu will appear. Select "System Preferences" from the drop-down menu.
Click the "Network" icon in the "Internet & Wireless" section. The Network window will appear.
Highlight "AirPort" in the left side of the Network window then click "Advanced" in the lower right corner.
Click the "AirPort" tab at the top of the window then scroll through the list of "Preferred Networks" and locate your network name.
Click on your network and then click the "Edit" icon that resembles a pencil next to the "+" and "-" icons below the list of preferred networks. A new window will appear.
Click in the "Password" field and delete the current password. Type the new password and click "OK." Note that you can place a check mark next to "Show password" to reveal the password currently saved for the selected Wi-Fi network.
Click the red "X" icon in the upper left corner of the window to exit the Network window and save your changes.
Highlight a preferred network from the Network window and click the "-" icon to force the computer to forget the network altogether.