I have a Linksys wireless 2.4 Ghz Broadband

Access the router setup page from the working computer you can do this by typing 192.168.1.1 on the address bar of your internet explorer and that will ask you for a username and password leave the username blank and password is admin if admin did not work type your commonly use password, Once you're on the setup page you can go to Wireless tab and then Wireless security and there enable the security that you want to use......