All routers are a litte different, but..
1. Click the wireless tab
2. then click "security" you should see a screen with a bunch of listings for WPA, WPA2, and WEP.
You should probably change the security to at least WPA.
1. Disable WEP
2. Enable WPA and enter a new password (pre shared key)....click apply
3. Rename the Network (just add a 1 behind the current network name) changing the network name is much easier than going to each computer and editing the connection settings....click apply (this might be under the wireless setup tab)
4. click save settings
5. click the network connections icon in the system tray, find your new network and click connect.
6. enter the new password
7. go to youtube and watch the "barking cat video"