connect onto the router with a cable to your computer/laptop and go to the routers IP address (usually 192.168.0.1 or 192.168.1.1 etc) and you should get a login page. The login details may be on a sticker on the router, if not may need to try the default password for the make of router. Once in, there will be a page/tab for the wireless key and you should be able to display it or change it.