You can check for the presence of the Airport card by going into System Profiler (I think that's the name, not sure because 10.2.3 is a bit old). Also, if the Airport wifi icon is not on the menu bar, go into your System Preferences, click Network, make sure the Airport network interface is enabled, and there should be a setting in there for displaying the Airport icon in the menu bar, that might not be turned on.
Once it appears, you should be able to click the Airport icon to reveal a menu with wifi networks within range, and select the name of your network in the list. It shouldn't be difficult. You should also be able to connect from inside the Network system preference, but using the Airport icon in the menu bar is easier.
Thanks for that
I checked that the airport card was installed properly as the system couldn't find it but now it is properly installed is won't start up at all - appears to boot up but then comes up with a message that I need to re-start it. When I do it just does the same again. Could this happen if the airport card is faulty?