1. Create Hash Password 
     echo -n "plaintext_password_here" | iconv -t utf16le | openssl md4
  2. Add WPA network details to /etc/wpa_supplicant/wpa_supplicant.conf file. 
     sudo vi /etc/wpa_supplicant/wpa_supplicant.conf
  3. Add wifi network details (and modify as per comment) 
     ## replace:
 ## ssid__name with the wifi SSID
 ## user__name with the wifi username
 ## the_hash with the hash password
 network={
   ssid="ssid__name"
   priority=1
   proto=RSN
   key_mgmt=WPA-EAP
   pairwise=CCMP
   auth_alg=OPEN
   eap=PEAP
   identity="user__name"
   password=hash:the_hash
   phase1="peaplabel=0"
   phase2="auth=MSCHAPV2"
 }
  4. Reconfigure WLAN interface 
     ## reconfigure; you should get OK as an output
 wpa_cli -i wlan0 reconfigure

Troubleshooting

work in progress

ifconfig wlan0
sudo iwlist wlan0 scan

# https://raspberrypi.stackexchange.com/a/123889
sudo killall wpa_supplicant
sudo wpa_supplicant -i wlan0 -D wext -c /etc/wpa_supplicant/wpa_supplicant.conf -B
wpa_cli -i wlan0 reconfigure

References