umm, who set up the wireless network in your house?
if it wasn't you then you should contact the person that did it, they'd be able to help you far better than us trying to guess what was done.
If not, typically for security there's a password required to connect to the wireless network, which is what I'm guessing that security ID is that you are being asked for.
I'm not sure what you mean by that you found a code on your router...
if that's a serial or model number it has no consequence on your connection to wireless network the router is serving