Wohoo, that was the easy bit getting is setup wired
Firstly you need to configure the router's wireless options, particularly the security settings. You should be able to browse from internet explorer on your wire connected PC to the admin pages of the router. probably 192.168.1.1 or similar (the manual should say). From there go to the wireless configuration. There should be options for SSID which is the name the router would broadcast. Choose something that you'd recognise, but which doesn't give away to much about where you are, say "myhomenet". You then need to setup the security. Depending on the options ideally use WEP2, or possibly WPA. You'll need to enter a preferred password.
Now you are ready for your wireless computer(s). Make sure the wireless card or adaptor is installed and enabled. If you haven't got the computer plugged into a wired connection it should start to scan for networks. If it doesn't right click on the network connections tab wireless and select the connect option. You should get the option to input your password. Hopefully that's it. If your lappy had any preconfigured internet connection settings make sure all that is set to auto.