Greetings Ladyhay. I am assuming you are on your own secured wireless network. Depending on the brand of wireless router you are using you can access it with the embedded web server. Open your browser and enter the router's IP address. This would look like http://[ipaddress]
Linksys routers use 192.168.1.1
D-Link and Netgear routers 192.168.0.1
US Robotics routers use 192.168.123.254
SMC routers use 192.168.2.1
From here you can access the setup utility and change the network key. You will then have to enter this new key on your computers.
Go to Network Connections, select properties of your Wireless Network Connection, click on the Wireless Networks tab, in the Preferred networks window highlight your network and then select Properties, here you will be able to enter the new network key.
I’ll check back a little later on your progress, good luck!
-John