How can I change my Network key to get onto my wireless network?

I have had my wireless network for a while now. It was installed for me and the guy who did it didn't tell me my network key. I now have a new laptop that want to connect to the network also, how can I do that without knowing what my network key is? Can I change it?How can I change my Network key to get onto my wireless network?
The default password to get into your router from here should be written on the back of the router.



go here and enter that user/password

http://192.168.1.1



This will log you into your router, you can change the network key settings from there.



if that doesnt work, try here



http://192.168.0.1





Note: If you can't log into the router, please post the brand and model number.