You should have specified what (wireless) network card/chip you have, it's an essential part of the problem. What part doesn't work - can't you find the program that lets you configure wireless networks, doesn't your wireless card (it's radio, really) power up, doesn't it accept your password for the network you're connecting to, can't it find any networks or what?
Google, and LQ (and other places) are full of wireless how-tos. If you know the exact problem (one of those I listed, for example), it's fairly easy to find a similar problem on the web, with a solution. Basically it boils town to:
1) there's no driver that works with the card or
2) there's no [read: I can't find a] program to configure the connection or
3) WEP encryption doesn't work
Solutions to these are generally
1) locate a working driver and install it; if it's about a Windows driver, ndiswrapper may (or may not) help
2) go trough your menus, or use iwlist and iwconfig
3) use wpa_supplicant, and read the instructions c-a-r-e-f-u-l-l-y
The wireless usage is somewhat general on nowadays Linux machines, especially if it's on Fedora/Ubuntu/Mandriva/Mepis/... so if you find a guide/howto for one of those, it most probably works for your distribution too - the only thing that may differ is the graphical user interface used (could be a KDE or Gnome app), but that's just a matter of placement of boxes and buttons, nothing you can't overcome