It is fairly self explanatory to do it through the UI if there is one but to do it through the terminal all you have to do is :

• sudo nano /etc/wpa_supplicant/wpa_supplicant.conf
• # Ensure it looks like

• country=GB
  ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
  update_config=1
  
  network={
      ssid="Errigal_WiFi"
      psk="PASSWORD"
  }

• save and exit
• Reboot and it should connect
• If having issues ensure your
• sudo nano /etc/network/interfaces
• looks like

• # interfaces(5) file used by ifup(8) and ifdown(8)
  
  # Please note that this file is written to be used with dhcpcd
  # For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'
  
  # Include files from /etc/network/interfaces.d:
  source-directory /etc/network/interfaces.d
  
  auto lo
  iface lo inet loopback
  
  iface eth0 inet manual
  
  allow-hotplug wlan0
  iface wlan0 inet manual
      wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
  
  allow-hotplug wlan1
  iface wlan1 inet manual
      wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf