Firstly, you need this :

http://www.ebuyer.com/UK/product/103185

and then one of these :

http://www.ebuyer.com/UK/product/118635

Ethernet cable comes out of broadband modem into your pc currently, that simply unplugs from pc and goes into the router. Suppied ethernet cable with router goes into pc and into router, wireless pcmcia card goes into laptop.

Setup the SSID network and get the laptop connected to it, then do the wireless security from the router via desktop pc. 10 min job