Ubuntu Wireless setup

Find your interface name

chili@T440p:~$ iwconfig
enp0s25   no wireless extensions.

lo        no wireless extensions.

wlp3s0    IEEE 802.11bgn  ESSID:"GBR1"  
          Mode:Managed  Frequency:2.462 GHz  Access Point: XX:2B:B0:DC:45:XX 
          Bit Rate=72.2 Mb/s   Tx-Power=22 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:on
          Link Quality=55/70  Signal level=-55 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:109   Missed beacon:0

It will be wlxxx something rather than wlan0 any more as it is 16.04 anyway.

Edit interface file

sudo vim /etc/network/interfaces

auto wlan0
iface wlan0 inet dhcp
wpa-ssid your_access_point
wpa-psk your_wpa_key

restart interface

sudo ifup -v wlxxx