They're talking about the "passphrase" that you set when you set up your wireless security. You will need to log onto your router, in the web GUI at 192.168.1.1, and go to where you set up the wireless security. Your wireless passphrase will be there.
If you don't remember how to log onto your router, you can go to the Linksys support site and download the user guide for your router and see if the default user/password there works for logging in. If not, and you don't remember the router password (not the same thing as your wireless security passphrase), then you'll need to do a factory reset on your router and re-enter your settings. At that point, you'll need to re-setup your wireless security, so you'll know what your wireless security passphrase is *smile*.
