First of all, it is much easier to connect to the internet through a network card then wireless.
Many wireless cards do not have drivers for linux.
You need to find out the type of wireless card and chipset for that card.
After you find all of that info, you can post a question at to the type of driver you will need. Or google for the proper driver.
After you get your card up and running, I suggest to install wicd wireless gui from slackbuilds.org to connect to networks.