Connect somputer to router by ethernet cable (one usually supplied with router). Dig out the literature which came with the router or download the manual from Linksys on how to address the router's user setup screens. Once in go to wireless security.
no problem , you can Secure your linksys router wrt54g using WPA and WEP
Click the Wireless Security sub-menu option at the top of the page. This is where we will provide the most important security setting.
Next to Security Mode, select WPA Personal from the drop-down list.(If you have trouble connecting to your linksys wrt54g connection, you can try selecting “WEP”, but your connection will be much less secure)
Next to WPA Algorithm, select AES. If you have trouble connecting to your wireless router, select TKIP.
Specify a long WPA Shared Key with a mix of upper and lower case letters, numbers and punctuation.you must get very creative.