What you should do is just edit file /etc/wpa_supplicant/wpa_supplicant.conf and add your WIFI information
sudo nano /etc/wpa_supplicant/wpa_supplicant.conf
You should add following text
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=GB
network={
ssid="insert_your_hidden_SSID_here"
scan_ssid=1
psk="insert_your_wifi_password_here"
key_mgmt=WPA-PSK
}