You need to log in to your router from your connected computer in your house. To get to the login screen you
type the router's ip address into the address field of your browser. It will be something like 192.168.1.1 or
192.168.2.1. You need the password for the router. If you never set a password it's given in the manual which is on the CD that came with the router or can be downloaded from the D-Link web site. The password might be, "admin".
Once logged in go to the wireless security page and you should see the WEP key given there.
dave