Just so you know, gnome and kde both can use networkmanager, but they use different applets to do so, and therefor have different icons. Gnomes is called, "network-manager-gnome", and kdes is called network-manager-kde. Point is, the icon will look different in kde. If i can remember correctly, it looks like a Ethernet port hole. Look down to your bottom right in your panel, in the system tray for it. I use kde but hate there network manager applet as it doesn't seem to have the capabilities of gnomes. I use mobile broadband and can't get it to work with kdes. If you still can't get wireless to work after the good people of this forum help you out, you can try the approach i use. Use the gnome network manager in kde. First uninstall the kde plasmoid network manager. (This step can be skipped obviously if you honestly don't have it) in the terminal, su to root and run,
aptitude remove network-manager-kde plasma-widget-networkmanagement
. This will remove the kde plasmoid network manager. Now open up kdes 'System Settings', go to the advanced tab up top, then to 'Autostart', press the 'add program button, type 'nm-applet' and press ok, restart and gnomes network manager applet should be down in your system tray.