Enable Wifi Dongle in Raspberrypi OSMC

Go to the command line interface of OSMC. Click the Power Icon. Select Exit, wait for the OSMC logo then press ESC.
Use username: osmc password: osmc

 Run the following Command:

 connmanctl  
 technologies  
 enable wifi  
 scan wifi  
 agent on  
 services  
 connect wifi_xxxxx #it will be a long string, hit tab for completion  

ref: https://osmc.tv/help/wiki/console
      https://discourse.osmc.tv/t/enable-wifi-under-gui/430/6