First make sure wifi is enables (on some laptops there is a switch for that, I don't know for yours).
Then type as root in a terminal:
ifconfig -a # you should see you wireless interface, probably names wlan0. If not, there is a problem to be solved
ifconfig # if the wireless interface shows in previous command but not in this one, bring it up with following command (tne try this one again to check)
ifconfig wlan0 up # replace wlan0 with the wireless interface name, if different
iwconfig # your wireless interface should show, probably as "not associated"
iwlist wlan0 scan # you should see the networks. Replace wlan0 with the wireless interface name, if different
I suggest you try wicd (available in /extra) which is very easy to use.