I connected to the internet now via my wirelesscard.
I downloaded the wpa_supplicant package but it seems a little bit difficult to configure it. I try to find on the slackbuild but the package doesn't exist there.
I solved my problem by take my wired NIC down and take my wireless NIC up the use "iwlist wlan0 scan" to scan for the ESSID, then I use "iwconfig wlan0 essid <id>" to connect to the wireless network.
It works fine this way. So I think I'll use it
.
Anyway, thanks for your help.