Hi arosha !
Open your Internet browser and enter your IP adress in the address bar: (http://192.168.1.1.
is the default ip for linksys wrt54g)
To login, By default the password is admin and leave the the user ID field blank.
click the Wireless tab then click Basic Wireless Settings ,next to Wireless SSID Broadcast, choose Disable. Then Click “Save Settings” .
This tip disable your linksys wrt54g from broadcasting your network name, or SSID. Computers can still access your network, but they'll need to know the network name - it won't appear automatically when they search for wireless networks.
You can You can change the SSID also from this screen. By default, your router sets the network name as "linksys," but you can change it to anything you want -. Beside the “Wireless Network Name (SSID)” option, type in a name for you network connection and click Save Settings