Configuring to SmartPlug Wireless Network - SSH Method

default /etc/config/wireless: 
...

config wifi-iface
        option device radio0
        option network lan
        option mode ap
        option ssid OK_SP3
        option encryption none

change /etc/config/wireless: 
...

config wifi-iface
        option device radio0
        option network wwan
        option ssid 'YOURSSID'
        option mode sta
        option encryption psk
        option key 'YOUR_WPA_KEY'

append /etc/config/network: (thanks Michael Liddle) 
  config interface 'wwan'
  option proto 'dhcp'

After saving this file, reboot the Smart Plug and it should be connected to your home network. If the connection fails, perform the "factory reset" procedures to reset the network settings. 
# reboot