These are the steps I followed to get my Raspberry Pi to see my hidden SSID.
Install iwlist
sudo iwlist wlan0 scan essid *yourSSID*
once you see the network Access Point, go to your wifi and find it listed, add it and enter your password/key
now, you are connected.
If you are working from the console screen and do not load Xwindow...
sudo nano /etc/network/interfaces
Edit the file and add/update these informaiton
allow-hotplug wlan0
auto wlan0
iface wlan0 inet manual
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
Now, you need to edit this file
sudo nano /etc/wpa_supplicant/wpa_supplicant.conf
Enter/Add the ssid information
network={
ssid="ssid-name"
psk="ssid-password"
key_mgmt=WPA-PSK
}
For key_mgmt, you need to find out what type it is, usually it is WPA-PSK
Reference:
https://www.raspberrypi.org/forums/viewtopic.php?&t=37119
