You'll probably have to do this on the laptop you have, I'm not sure it will work from the desktop (with a USB connection)
Click the link below
http://192.168.0.1
Login using the details printed on the back of the superhub, click on the wireless settings button and you should be able to change the password there.
When you change the password you'll lose connection with the laptop and you'll have to reconnect to the wireless network with the new password.