You either go to where you wrote it down or you go into the router's
configuration screens. From a computer directly attached to the router
(wired), put the router's IP address in a browser addressbar. Example
for a Linksys:
Put in the username/password and go to the wireless settings. You'll see
your key there. If you didn't change the username/password but don't
remember it, refer to the router's manual for the default settings.
